What do you know about Java?
What are the supported platforms
by Java Programming Language?
List any five features of Java?
Why is Java Architectural
Neutral?
How Java enabled High
Performance?
Why Java is considered dynamic?
What is Java Virtual Machine and
how it is considered in context of Java’s platform independent feature?
List two Java IDE’s?
List some Java keywords(unlike
C, C++ keywords)?
What do you mean by Object?
Define class?
What kind of variables a class
can consist of?
What is a Local Variable?
What is a Instance Variable?
What is a Class Variable?
What is Singleton class?
What do you mean by Constructor?
List the three steps for
creating an Object for a class?
What is the default value of
byte datatype in Java?
What is the default value of float
and double datatype in Java?
When a byte datatype is used?
What is a static variable?
What do you mean by Access
Modifier?
What is protected access
modifier?
What do you mean by synchronized
Non Access Modifier?
According to Java Operator
precedence, which operator is considered to be with highest precedence?
Variables used in a switch
statement can be used with which datatypes?
When parseInt() method can be
used?
Why is String class considered
immutable?
Why is StringBuffer called
mutable?
What is the difference between
StringBuffer and StringBuilder class?
Which package is used for
pattern matching with regular expressions?
java.util.regex consists of
which classes?
What is finalize() method?
What is an Exception?
What do you mean by Checked
Exceptions?
Explain Runtime Exceptions?
Which are the two subclasses
under Exception class?
When throws keyword is used?
When throw keyword is used?
How finally used under Exception
Handling?
What things should be kept in
mind while creating your own exceptions in Java?
Define Inheritance?
When super keyword is used?
What is Polymorphism?
What is Abstraction?
What is Abstract class?
When Abstract methods are used?
What is Encapsulation?
What is the primary benefit of
Encapsulation?
What is an Interface?
Give some features of Interface?
Define Packages in Java?
Why Packages are used?
What do you mean by
Multithreaded program?
What are the two ways in which
Thread can be created?
What is an applet?
An applet extend which class?
Explain garbage collection in Java?
Define immutable object?
Explain the usage of this() with
constructors?
Explain Set Interface?
Explain TreeSet?
What is Comparable Interface?
Difference between throw and
throws?
Explain the following line used
under Java Program:
public static void main (String
args[ ])
Define JRE i.e. Java Runtime
Environment?
What is JAR file?
What is a WAR file?
Define JIT compiler?
What is the difference between
object oriented programming language and object based programming language?
What is the purpose of default
constructor?
Can a constructor be made final?
What is static block?
Define composition?
What is function overloading?
What is function overriding?
Difference between Overloading
and Overriding?
What is final class?
What is NullPointerException?
What are the ways in which a
thread can enter the waiting state?
How does multi-threading take
place on a computer with a single CPU?
What invokes a thread's run()
method?
Does it matter in what order
catch statements for FileNotFoundException and IOException are written?
What is the difference between
yielding and sleeping?
Why Vector class is used?
How many bits are used to
represent Unicode, ASCII, UTF-16, and UTF-8 characters?
What are Wrapper classes?
What is the difference between a
Window and a Frame?
Which package has light weight
components?
What is the difference between
the paint() and repaint() methods?
What is the purpose of File
class?
What is the difference between
the Reader/Writer class hierarchy and the InputStream/OutputStream class
hierarchy?
Which class should you use to
obtain design information about an object?
What is the difference between
static and non-static variables?
What is Serialization and
deserialization?
What are use cases?
Explain the use of sublass in a
Java program?
How to add menushortcut to menu
item?
Can you write a Java class that
could be used both as an applet as well as an application?
What is the difference between
Swing and AWT components?
What's the difference between
constructors and other methods?
Is there any limitation of using
Inheritance?
When is the ArrayStoreException
thrown?
Can you call one constructor
from another if a class has multiple constructors?
What's the difference between
the methods sleep() and wait()?
When ArithmeticException is
thrown?
What is a transient variable?
What is synchronization?
What is the Collections API?
Does garbage collection
guarantee that a program will not run out of memory?
The immediate superclass of the
Applet class?
Which Java operator is right
associative?
What is the difference between a
break statement and a continue statement?
If a variable is declared as
private, where may the variable be accessed?
What is the purpose of the
System class?
List primitive Java types?
What is the relationship between
clipping and repainting under AWT?
Which class is the immediate
superclass of the Container class?
What class of exceptions are
generated by the Java run-time system?
Under what conditions is an
object's finalize() method invoked by the garbage collector?
How can a dead thread be
restarted?
Which arithmetic operations can
result in the throwing of an ArithmeticException?
Variable of the boolean type is
automatically initialized as?
Can try statements be nested?
What are ClassLoaders?
What is the difference between
an Interface and an Abstract class?
What will happen if static
modifier is removed from the signature of the main method?
What is the default value of an
object reference declared as an instance variable?
Can a top level class be private
or protected?
Why do we need wrapper classes?
What is the difference between
error and an exception?
Is it necessary that each try
block must be followed by a catch block?
When a thread is created and
started, what is its initial state?
What is the Locale class?
What are synchronized methods
and synchronized statements?
What is runtime polymorphism or
dynamic method dispatch?
What is Dynamic Binding(late
binding)?
Can constructor be inherited?
What are the advantages of
ArrayList over arrays?
Why deletion in LinkedList is
fast than ArrayList?
How do you decide when to use
ArrayList and LinkedList?
What is a Values Collection View
?
What is dot operator?
Where and how can you use a
private constructor?
What is type casting?
Describe life cycle of thread?
What is the difference between
the >> and >>> operators?
Which method of the Component
class is used to set the position and size of a component?
What is the range of the short
type?
What is the immediate superclass
of Menu?
Does Java allow Default
Arguments?
Which number is denoted by
leading zero in java?
Which number is denoted by
leading 0x or 0X in java?
Break statement can be used as
labels in Java?
Where import statement is used
in a Java program?
Explain suspend() method under
Thread class>
Explain isAlive() method under Thread
class?
What is currentThread()?
Explain main thread under Thread
class execution?
Life cycle of an applet includes
which steps?
Why is the role of init() method
under applets?
Which method is called by Applet
class to load an image?
Define code as an attribute of
Applet?
Define canvas?
Define Network Programming?
What is a Socket?
Advantages of Java Sockets?
Disadvantages of Java Sockets?
Which class is used by server
applications to obtain a port and listen for client requests?
Which class represents the
socket that both the client and server use to communicate with each other?
Why Generics are used in Java?
What environment variables do I
need to set on my machine in order to be able to run Java programs?
Is there any need to import
java.lang package?
What is Nested top-level class?
What is Externalizable
interface?
If System.exit (0); is written
at the end of the try block, will the finally block still execute?
What is daemon thread?
Which method is used to create
the daemon thread?
Which method must be implemented
by all threads?
What is the GregorianCalendar
class?
What is the SimpleTimeZone
class?
What is the difference between
the size and capacity of a Vector?
Can a vector contain
heterogenous objects?
What is an enumeration?
What is difference between Path
and Classpath?
Can a class declared as private
be accessed outside it's package?
What are the restriction imposed
on a static method or a static block of code?
Can an Interface extend another
Interface?
Which object oriented Concept is
achieved by using overloading and overriding?
What is an object's lock and
which object's have locks?
What is Downcasting?
What are order of precedence and
associativity and how are they used?
If a method is declared as
protected, where may the method be accessed?
What is the difference between
inner class and nested class?
What restrictions are placed on
method overriding?
What is constructor chaining and
how is it achieved in Java?
Can a double value be cast to a
byte?
How does a try statement
determine which catch clause should be used to handle an exception?
What will be the default values
of all the elements of an array defined as an instance variable?
buggybread
Q1. What is a cookie ?
Q2. Can we reduce the visibility
of the overridden method ?
Q3. What are different types of
inner classes ?
Q4. Difference between TreeMap
and HashMap ?
Q5. What is the difference
between List, Set and Map ?
Q6. Difference between Public, Private,
Default and Protected ?
Q7. What is servlet Chaining ?
Q8. What are the Wrapper classes
available for primitive types ?
Q9. What are concepts introduced
with Java 5 ?
Q10. Does Constructor creates
the object ?
Q11. Can static method access
instance variables ?
Q12. Does Java support Multiple
Inheritance ?
Q13. Difference between == and
.equals() ?
Q14. Difference between Checked
and Unchecked exceptions ?
Q15. What is a Final Variable ?
Q16. Which class does not
override the equals() and hashCode() methods, inheriting them directly from
class Object?
Q17. What is a final method ?
Q18. Which interface does
java.util.Hashtable implement?
Q19. What is an Iterator?
Q20. Which interface provides
the capability to store objects using a key-value pair?
Q21. Difference between HashMap
and Hashtable?
Q22. Does java allow overriding
static methods ?
Q23. When are static variables
loaded in memory ?
Q24. Can we serialize static
variables ?
Q25. What will this code print ?
String a = new String
("TEST");
String b = new String
("TEST");
if(a == b) {
System.out.println
("TRUE");
} else {
System.out.println
("FALSE");
}
Q26. There are two objects a and
b with same hashcode. I am inserting these two objects inside a hashmap.
hMap.put(a,a);
hMap.put(b,b);
where a.hashCode()==b.hashCode()
Now tell me how many objects
will be there inside the hashmap?
Q27. Difference between
long.Class and Long.TYPE ?
Q28. Does Java provides default
copy constructor ?
Q29. What are the common uses of
"this" keyword in java ?
Q30. What are the difference
between Threads and Processes ?
Q31. How can we run a java program
without making any object?
Q32. Explain multithreading in
Java ?
Q33. Can constructors be
synchronized in Java ?
Q34. can we create a null as a
key for a map collection ?
Q35. What is the use of hashcode
in Java ?
Q36. Why java doesn't support
multiple Inheritence ?
Q37. Why threads block or enters
to waiting state on I/O?
Q38. What are transient
variables in java?
Q39. What is the difference
between yield() and sleep()?
Q40. What are wrapper classes ?
Q41. What is the difference
between time slicing and preemptive scheduling ?
Q42. What is the initial state
of a thread when it is created and started?
Q43. What one should take care
of, while serializing the object?
Q44. What is a String Pool ?
Q45. Why is String immutable in
Java ?
Q46. what is the use of cookie
and session ? and What is the difference between them ?
Q47. Which are the different
segments of memory ?
Q48. Which memory segment loads
the java code ?
Q49. which containers use a
border Layout as their default layout ?
Q50. Can a lock be acquired on a
class ?
Q51. What state does a thread
enter when it terminates its processing?
Q52. How many bits are used to
represent Unicode, ASCII, UTF-16, and UTF-8 characters?
Q53. Does garbage collection
guarantee that a program will not run out of memory?
Q54. What is an object's lock
and which object's have locks?
Q55. What is casting?
Q56. What restrictions are
placed on method overriding?
Q57. How does a try statement
determine which catch clause should be used to handle an exception?
Q58. Describe what happens when
an object is created in Java ?
Q59. What is the difference
between StringBuffer and String class ?
Q60. Describe, in general, how
java's garbage collector works ?
Q61. What is RMI ?
Q62. What is JDBC? Describe the
steps needed to execute a SQL query using JDBC.
Q63. Are constructors inherited?
Can a subclass call the parent's class constructor? When?
Q64. What is JSON ?
Q65. What is the role of
JSON.stringify ?
Q66. When were Enums introduced
in Java ?
Q67. Which function is used to
convert a JSON text into an object ?
Q68. Which data types are
supported by JSON ?
Q69. What are the benefits of
JSON over XML ?
Q70. What are the methods of
Object Class ?
Q71. Explain JMS ( Java
Messaging Services ) ?
Q72. Explain EJB (Enterprise
Java Beans) ?
Q73. Which MVC is struts2 based
on ?
Q74. What is an API (
Application Programming Interface ) ?
Q75. What is URL?
Q76. Explain features of struts2
?
Q77. What is HTTP ?
Q78. what is content
negotiation?
Q79. Is tomcat an application or
Web server ?
Q80. Is Apache an application or
Web server
Q81. What are the default or
implicitly assigned values for data types in java ?
Q82. What is difference between
Encapsulation And Abstraction?
Q83. Can I import same
package/class twice? Will the JVM load the package twice at runtime?
Q84. Explain static blocks in
Java ?
Q85. Which access specifier can
be used with Class ?
Q86. Explain Annotations ?
Q87. Give an Example of
Annotations ?
Q88. What are few of the Annotations
pre defined by Java?
Q89. What are meta Annotations ?
Q90. Name few meta-annotations ?
Q91. How to display and set the
Class path in Unix ?
Q92. Difference between Abstract
and Concrete Class ?
Q93. Difference between
Overloading and Overriding ?
Q94. Difference between Vector
and ArrayList ?
Q95. Different ways of
implementing Threads in Java ?
Q96. What is Volatile keyword
used for ?
Q97. Whatis Serialization ?
Q98. What is the use of
Transient Keyword ?
Q99. What is a final variable ?
Q100. What is a Final Method ?
Q101. What is a Final Class ?
Q102. What is an Immutable
Object ?
Q103. What is an immutable class
?
Q104. How to implement an
immutable class ?
Q105. Does Declaring an object
"final" makes it immutable ?
Q106. Difference between object
instantiation and construction ?
Q107. Can we override static
methods ? Why ?
Q108. Can we access instance
variables within static methods ?
Q109. Can we reduce the
visibility of the inherited or overridden method ?
Q110. Give an Example of checked
and unchecked exception ?
Q111. Name few Java Exceptions ?
Q112. Which of the following is
tightly bound ? Inheritance or Composition ?
Q113. How can we make sure that
a code segment gets executed even in case of uncatched exceptions ?
Q114. Explain the use of
"Native" keyword ?
Q115. What is "super"
used for ?
Q116. What is "this"
keyword used for ?
Q117. Difference between boolean
and Boolean ?
Q118. What is a finalize method
?
Q119. What are Marker Interfaces
? Name few Java marker interfaces ?
Q120. Is runnable a Marker
interface ?
Q121. Difference between Process
and Thread ?
Q122. Wha is a Deadlock ?
Q123. Difference between Serialization
and Deserialization ?
Q124. Explain Autoboxing ?
Q125. What is an Enum type ?
Q126. What are Wrapper Classes ?
What are Primitive Wrapper Classes ?
Q127. What Design pattern
Wrapper Classes implement ?
Q128. What is "Import"
used for ?
Q129. Different types of memory
used by JVM ?
Q130. What is a class loader ?
What are the different class loaders used by JVM ?
Q131. Can we declare interface methods
as private ?
Q132. What is a Static import ?
Q133. Difference between
StringBuffer and StringBuilder ?
Q134. Difference between Map and
HashMap ?
Q135. What is a Property class ?
Q136. Explain the scenerios to
choose between String , StringBuilder and StringBuffer ?
Q137. Explain
java.lang.OutOfMemoryError ?
Q138. Can we have multiple
servlets in a web application and How can we do that ?
Q139. How can we manage Error
Messages in the web application ?
Q140. Is JVM, a compiler or
interpretor ?
Q141. Difference between implicit
and explicit type casting ?
Q142. Difference between
loadClass and Class.forName ?
Q143. Should we override
finalize method ?
Q144. What is assert keyword
used for ?
Q145. Difference between Factory
and Abstract Factory Design Pattern ?
Q146. Difference between Factory
and Builder Design Pattern ?
Q147. Difference between Proxy
and Adapter ?
Q148. Difference between Adapter
and Facade ?
Q149. Difference between Builder
and Composite ?
Q150. Example of Chain of Responsibility
Design Pattern ?
Q151. Example of Observer Design
Pattern ?
Q152. Difference between Factory
and Strategy Design Pattern ?
Q153. Shall we use abstract
classes or Interfaces in Policy / Strategy Design Pattern ?
Q154. Which kind of memory is
used for storing object member variables and function local variables ?
Q155. Why do member variables
have default values whereas local variables don't have any default value ?
Q156. What is a Default
Constructor ?
Q157. Will Compiler creates a
default no argument constructor if we specify only multi argument constructor ?
Q158. Can we overload
constructors ?
Q159. What will happen if we
make the constructor private ?
Q160. How can we create objects
if we make the constructor private ?
Q161. What will happen if we
remove the static keyword from main method ?
Q162. Why Java don't use
pointers ?
Q163. Can we use both
"this" and "super" in a constructor ?
Q164. Do we need to import
java.lang.package ?
Q165. Is it necessary that each
try block to be followed by catch block ?
Q166. Can finally block be used
without catch ?
Q167. What is exception
propogation ?
Q168. Difference between nested
and inner classes ?
Q169. What is a nested interface
?
Q170. What is an Externalizable
interface ?
Q171. Difference between
serializable and externalizable interface ?
Q172. What is reflection ?
Q173. Can we instantiate the
object of derived class if parent constructor is protected ?
Q174. Can we declare an abstract
method private ?
Q175. What are the design
considerations while making a choice between using interface and abstract class
?
Q176. What is a config Object?
Q177. What is a pageContext Object?
Q178. What is suspend() method
used for ?
Q179. Difference between suspend()
and stop() ?
Q180. What are the benefits of
using Spring Framework ?
Q181. what is the difference
between collections class vs collections interface ?
Q182. Will this code give error
if i try to add two heterogeneous elements in the arraylist. ? and Why ?
List list1 = new
ArrayList<>();
list1.add(5);
list1.add("5");
Q183. Difference between Java
beans and Spring Beans ?
Q184. What is the difference
between System.console.write and System.out.println ?
Q185. What are various types of
Class loaders used by JVM ?
Q186. How are classes loaded by
JVM ?
Q187. Difference between C++ and
Java ?
Q188. Difference between static
vs. dynamic class loading?
Q189. Tell something about
BufferedWriter ? What are flush() and close() used for ?
Q190. What is Scanner class used
for ? when was it introduced in Java ?
Q191. Why Struts 1 Classes are
not Thread Safe whereas Struts 2 classes are thread safe ?
Q192. What are some Java related
technologies used for distributed computing ?
Q193. Whats the purpose of
marker interfaces ?
Q194. What is the difference
between final, finally and finalize() ?
Q195. When do you get
ClassCastException?
Q196. Explain Thread States ?
Q197. What are strong, soft,
weak and phantom references in Java ?
Q198. Difference between yield()
and sleeping()?
Q199. What is a daemon thread?
Give an Example ?
Q200. What is the difference between
AWT and Swing?
Q201. What is the order of
method invocation in an applet?
Q202. Name few tools for probing
Java Memory Leaks ?
Q203. Which memory areas does
instance and static variables use ?
Q204. What is J2EE? What are
J2EE components and services?
Q205. What are the components of
J2EE ?
Q206. What is XML ?
Q207. Difference between SAX and
DOM Parser ?
Q208. What is DTD ?
Q209. What is XSD ?
Q210. What is JAXP ?
Q211. What is JAXB ?
Q212. What is marshalling ?
Q213. What is unmarshalling ?
Q214. Which load testing tools
have you used ?
Q215. What are LDAP servers used
for ?
Q216. What is the difference
between comparable and comparator in java.util pkg?
Q217. What are different modules
of spring ?
Q218. Explain Flow of Spring MVC
?
Q219. What is Spring
configuration file?
Q220. Q: What is default scope
of bean in Spring framework?
Q221. What bean scopes does
Spring support? Explain them.
Q222. What is bean auto wiring?
Q223. Difference between socket
and servlet ?
Q224. Difference Between this()
and super() ?
Q225. What are the phases of the
JSP life cycle ?
Q226. Difference between the jsp
scriptlet tag and jsp declaration tag?
Q227. What are JSP directives ?
What are different types of directives ?
Q228. What is Java bytecode ?
Q229. What is a Listener ?
Q230. What is MVC ?
Q231. What is race condition ?
Q232. What is unicode ?
Q233. What is ThreadFactory ?
Q234. What is PermGen or Permanent
Generation ?
Q235. What is metaspace ?
Q236. What is the benefit of
inner / nested classes ?
Q237. Explain Static nested Classes
?
Q238. Explain Inner Classes ?
Q239. Explain Method Local Inner
Classes ?
Q240. Explain about anonymous
inner classes ?
Q241. What will happen if class
implement two interface having common method?
Q242. What is the advantage of
using arrays over variables ?
Q243. What are the disadvantages
of using arrays ?
Q244. Difference between
Class#getInstance() and new operator ?
Q245. Can we create an object if
a Class doesn't have any constructor ( not even the default provided by
constructor ) ?
Q246. What is a cloneable
interface and what all methods does it contain?
Q247. When you will synchronize
a piece of your code?
Q248. Are there any global
variables in Java, which can be accessed by other part of your program?
Q249. What is an applet? What is
the lifecycle of an applet?
Q250. What is meant by controls
and what are different types of controls in AWT / SWT?
Q251. What is a stream and what
are the types of Streams and classes of the Streams?
Q252. What is session tracking
and how do you track a user session in servlets?
Q253. What is connection
pooling?
Q254. Advantage of Collection classes
over Arrays ?
Q255. What are the Disadvantages
of using Collection Classes over Arrays ?
Q256. Can we call constructor
explicitly ?
Q257. Does a class inherit the
constructor of its super class?
Q258. What is the difference
between float and double?
Q259. What is the difference between
>> and >>>?
Q260. What is the difference
between System.out ,System.err and System.in?
Q261. Is it possible to compile
and run a Java program without writing main( ) method?
Q262. What are different ways of
object creation in Java ?
Q263. What is Generalization and
Specialization in terms of casting ?
Q264. Can we call the garbage
collector explicitly ?
Q265. How does volatile affect
code optimization by compiler?
Q266. Do you think that Java
should have had pointers ?
Q267. How would you go about debugging
a NullPointerException?
Q268. How does Java differ from
other programming languages you've worked with?
Q269. Should good code be
self-documenting, or is it the responsibility of the developer to document it?
Q270. What are points to
consider in terms of access modifier when we are overriding any method?
Q271. what is covariant return
type?
Q272. How compiler handles the
exceptions in overriding ?
Q273. Why is Java considered
Portable Language ?
Q274. Tell something about
history of Java ?
Q275. How to find if JVM is 32
or 64 bit from Java program. ?
Q276. Does every class needs to
have one non parameterized constructor ?
Q277. Difference between throw
and throws ?
Q278. Can we use
"this" within static method ? Why ?
Q279. Similarity and Difference
between static block and static method ?
Q280. What are the platforms
supported by Java Programming Language?
Q281. How Java provide high
Performance ?
Q282. What is IDE ? List few
Java IDE ?
Q283. What is an Object ?
Q284. What is a Class ?
Q285. According to Java Operator
precedence, which operator is considered to be with highest precedence?
Q286. What data type Variable
can be used in a switch statement ?
Q287. What are the sub classes
of Exception class?
Q288. How finally used under
Exception Handling?
Q289. What things should be kept
in mind while creating your own exceptions in Java?
Q290. What is Comparable
Interface?
Q291. Explain Set Interface?
Q292. What is the difference
between the Reader/Writer class hierarchy and the InputStream/OutputStream
class hierarchy?
Q293. What are use cases?
Q294. Which Java operator is
right associative?
Q295. What is the difference
between a break statement and a continue statement?
Q296. What is the purpose of the
System class?
Q297. Variable of the boolean
type is automatically initialized as?
Q298. Can try statements be
nested?
Q299. What will happen if static
modifier is removed from the signature of the main method?
Q300. What is the Locale class?
Q301. Define Network
Programming?
Q302. What are the advantages and
Disadvantages of Sockets ?
Q303. What environment variables
do I need to set on my machine in order to be able to run Java programs?
Q304. What is Externalizable
interface?
Q305. What is the difference
between the size and capacity of a Vector?
Q306. What is an enum or
enumeration?
Q307. What is constructor
chaining and how is it achieved in Java?
Q308. What is the best practice
configuration usage for files - pom.xml or settings.xml ?
Q309. Why Java provides default
constructor ?
Q310. In a case where there are
no instance variables what does the default constructor initialize?
Q311. How can I change the
default location of the generated jar when I command "mvn package"?
Q312. What is Maven's order of
inheritance?
Q313. What is a Mojo?
Q314. How do I determine which
POM contains missing transitive dependency?
Q315. Difference between
Encapsulation and Data Hiding ?
Q316. Difference between
Abstraction and Implementation hiding ?
Q317. What are the features of
encapsulation ?
Q318. What are the examples of Abstraction
in Java ?
Q319. What are different ways to
create String Object? Explain.
Q320. Write a method to check if
input String is Palindrome?
Q321. Write a method that will
remove given character from the String?
Q322. Which String class methods
are used to make string upper case or lower case?
Q323. How to convert String to
byte array and vice versa?
Q324. Why Char array is
preferred over String for storing password?
Q325. Why String is popular
HashMap key in Java?
Q326. What ate the getter and
setter methods ?
Q327. public class a {
public static void main(String
args[]){
final String s1="job";
final String
s2="seeker";
String s3=s1.concat(s2);
String s4="jobseeker";
System.out.println(s3==s4); //
Output 1
System.out.println(s3.hashCode()==s4.hashCode());
Output 2
}
}
What will be the Output 1 and
Output 2 ?
Q328. What is the use of
HashCode in objects ?
Q329. Difference between
Compositions and Inheritance ?
Q330. Will finally be called
always if all code has been kept in try block ?
Q331. Will the static block be
executed in the following code ? Why ?
class Test
{
static
{
System.out.println("Why I
am not executing ");
}
public static final int
param=20;
}
public class Demo
{
public static void main(String[]
args)
{
System.out.println(Test.param);
}
}
Q332. Will static block for Test
Class execute in the following code ?
class Test
{
static
{
System.out.println("Executing
Static Block.");
}
public final int param=20;
public int getParam(){
return param;
}
}
public class Demo
{
public static void main(String[]
args)
{
System.out.println(new
Test().param);
}
}
Q333. What does String intern()
method do?
Q334. Will the following program
display "Buggy Bread" ?
class Test{
static void display(){
System.out.println("Buggy
Bread");
}
}
class Demo{
public static void
main(String... args){
Test t = null;
t.display();
}
}
Q335. How substring() method of
String class create memory leaks?
Q336. Write a program to reverse
a string iteratively and recursively ?
Q337. If you have access to a
function that returns a random integer from one to five, write another function
which returns a random integer from one to seven.
Q338. Write a method to convert
binary to a number ?
Q339. What will the following
code print ?
String s1 = "Buggy
Bread";
String s2 = "Buggy
Bread";
if(s1 == s2)
System.out.println("equal
1");
String n1 = new
String("Buggy Bread");
String n2 = new
String("Buggy Bread");
if(n1 == n2)
System.out.println("equal
2");
Q340. Difference between new
operator and Class.forName().newInstance() ?
Q341. What is Java bytecode ?
Q342. How to find whether a
given integer is odd or even without use of modules operator in java?
Q343. Is JVM a overhead ?
Q344. Can we use Ordered Set for
performing Binary Search ?
Q345. What is Byte Code ? Why
Java's intermediary Code is called Byte Code ?
Q346. Difference between
ArrayList and LinkedList ?
Q347. If you are given a choice
to use either ArrayList and LinkedList, Which one would you use and Why ?
Q348. What are the pre-requisite
for the collection to perform Binary Search ?
Q349. Can you provide some
implementation of a Dictionary having large number of words ?
Q350. Difference between PATH
and CLASSPATH ?
Q351. Name few access and non
access Class Modifiers ?
Q352. Which Java collection
class can be used to maintain the entries in the order in which they were last
accessed?
Q353. Is it legal to initialize
List like this ?
LinkedList l=new LinkedList();
Q354. Which of the following
syntax is correct ?
import static java.lang.System.*;
or
static import
java.lang.System.*;
Q355. What will be the output of
following code ?
public static void main(String[]
args)
{
int x = 10;
int y;
if (x < 100) y = x / 0;
if (x >= 100) y = x * 0;
System.out.println("The
value of y is: " + y);
}
Q356. What will be the output of
following Code ?
class BuggyBread {
public static void main(String[]
args)
{
String s2 = "I am
unique!";
String s5 = "I am
unique!";
System.out.println(s2 == s5);
}
}
Q357. What will be the output of
following code ?
class BuggyBread2 {
private static int counter = 0;
void BuggyBread2() {
counter = 5;
}
BuggyBread2(int x){
counter = x;
}
public static void main(String[]
args) {
BuggyBread2 bg = new
BuggyBread2();
System.out.println(counter);
}
}
Q358. What will be the output of
following code ?
class BuggyBread1 {
public String method() {
return "Base Class -
BuggyBread1";
}
}
class BuggyBread2 extends
BuggyBread1{
private static int counter = 0;
public String method(int x) {
return "Derived Class -
BuggyBread2";
}
public static void main(String[]
args) {
BuggyBread1 bg = new
BuggyBread2();
System.out.println(bg.method());
}
}
Q359. What are RESTful Web
Services ?
Q360. Which markup languages can
be used in restful web services ?
Q361. Difference between Inner
and Outer Join ?
Q362. What is a Cursor ?
Q363. What is database deadlock
? How can we avoid them?
Q364. What are temp tables ?
365. Why Web services use HTTP
as the communication protocol ?
Q366. what will be the output of
this code ?
public static void main(String[]
args)
{
StringBuffer s1=new
StringBuffer("Buggy");
test(s1);
System.out.println(s1);
}
private static void
test(StringBuffer s){
s.append("Bread");
}
Q367. what will be the output of
this code ?
public static void main(String[]
args)
{
String s1=new
String("Buggy");
test(s1);
System.out.println(s1);
}
private static void
test(StringBuffer s){
s.append("Bread");
}
Q368. what will be the output of
this code ?
public static void main(String[]
args)
{
StringBuffer s1=new
StringBuffer("Buggy");
test(s1);
System.out.println(s1);
}
private static void
test(StringBuffer s){
s=new
StringBuffer("Bread");
}
Q369. what will be the output ?
class Animal {
public void eat() throws
Exception {
}
}
class Dog2 extends Animal {
public void eat(){}
public static void main(){
Animal an = new Dog2();
an.eat();
}
}
Q370. What are advantages of
using Servlets over CGI ?
Q371. gfdddddddddddddddddddddddd
Q372. Does SQL allow null values
? Can we use it within Where clause ?
Q373. Can we add duplicate keys
in a HashMap ? What will happen if we attempt to add duplicate values ?
Q374. What is the use of
HTTPSession in relation to http protocol ?
Q375. Why using cookie to store
session info is a better idea than just using session info in the request ?
Q376. What are different types
of cookies ?
Q377. http protocol is by
default ... ?
Q378. Can finally block throw an
exception ?
Q379. Can we have try and catch
blocks within finally ?
Q380. Which of the following is
a canonical path ?
1.
C:\directory\..\directory\file.txt
2. C:\directory\subDirectory1\directory\file.txt
3. \directory\file.txt
Q381. What will the following
code print when executed on Windows ?
public static void main(String[]
args){
String parent = null;
File file = new
File("/file.txt");
System.out.println(file.getPath());
System.out.println(file.getAbsolutePath());
try {
System.out.println(file.getCanonicalPath());
} catch (IOException e) {
// TODO Auto-generated catch
block
e.printStackTrace();
}
}
Q382. What will be the output of
following code ?
public static void main(String[]
args){
String name = null;
File file = new
File("/folder", name);
System.out.print(file.exists());
}
Q383. What will be the output of
following code ?
public static void main(String[]
args){
String parent = null;
File file = new File(parent,
"myfile.txt");
try {
file.createNewFile();
} catch (IOException e) {
// TODO Auto-generated catch
block
e.printStackTrace();
}
}
Q384. What will be the output of
following code ?
public static void main(String[]
args){
String child = null;
File file = new
File("/folder", child);
try {
file.createNewFile();
} catch (IOException e) {
// TODO Auto-generated catch
block
e.printStackTrace();
}
}
Q385. What will be the output of
following code, assuming that currently we are in c:\Project ?
public static void main(String[]
args){
String child = null;
File file = new
File("../file.txt");
System.out.println(file.getPath());
System.out.println(file.getAbsolutePath());
try {
System.out.println(file.getCanonicalPath());
} catch (IOException e) {
// TODO Auto-generated catch
block
e.printStackTrace();
}
}
Q386. Which is the abstract
parent class of FileWriter ?
Q387. Which class is used to
read streams of characters from a file?
Q388. Which class is used to
read streams of raw bytes from a file?
Q389. Which is the Parent class
of FileInputStream ?
Q390. Which of the following
code is correct ?
FileWriter fileWriter = new
FileWriter("../file.txt");
File file = new File(fileWriter
);
BufferedWriter
bufferedOutputWriter = new BufferedWriter(fileWriter);
b.
BufferedWriter
bufferedOutputWriter = new BufferedWriter("../file.txt");
File file = new
File(bufferedOutputWriter );
FileWriter fileWriter = new
FileWriter(file);
c.
File file = new
File("../file.txt");
FileWriter fileWriter = new
FileWriter(file);
BufferedWriter
bufferedOutputWriter = new BufferedWriter(fileWriter);
d.
File file = new
File("../file.txt");
BufferedWriter
bufferedOutputWriter = new BufferedWriter(file);
FileWriter fileWriter = new
FileWriter(bufferedOutputWriter );
Q391. Which exception should be handled
in the following code ?
File file = new
File("../file.txt");
FileWriter fileWriter = new
FileWriter(file);
Q392. Which exceptions should be
handled with the following code ?
FileOutputStream
fileOutputStream = new FileOutputStream(new File("newFile.txt"));
Q393. Will this code compile
fine ?
ObjectOutputStream
objectOutputStream = new ObjectOutputStream(new FileOutputStream(new File("newFile.txt")));
Q394. What is the problem with
this code ?
class BuggyBread1 {
private BuggyBread2 buggybread2;
public static void main(String[]
args){
try {
BuggyBread1 buggybread1 = new
BuggyBread1();
ObjectOutputStream
objectOutputStream = new ObjectOutputStream(new FileOutputStream(new
File("newFile.txt")));
objectOutputStream.writeObject(buggybread1);
} catch (Exception e) {
// TODO Auto-generated catch
block
e.printStackTrace();
}
}
}
Q395. Will this code run fine if
BuggyBread2 doesn't implement Serializable interface ?
class BuggyBread1 implements
Serializable{
private BuggyBread2 buggybread2
= new BuggyBread2();
public static void main(String[]
args){
try {
BuggyBread1 buggybread1 = new
BuggyBread1();
ObjectOutputStream
objectOutputStream = new ObjectOutputStream(new FileOutputStream(new
File("newFile.txt")));
objectOutputStream.writeObject(buggybread1);
} catch (Exception e) {
// TODO Auto-generated catch
block
e.printStackTrace();
}
}
}
Q396. Will this code work fine
if BuggyBread2 doesn't implement Serializable ?
class BuggyBread1 extends BuggyBread2
implements Serializable{
private int x = 5;
public static void main(String[]
args){
try {
BuggyBread1 buggybread1 = new
BuggyBread1();
ObjectOutputStream
objectOutputStream = new ObjectOutputStream(new FileOutputStream(new
File("newFile.txt")));
objectOutputStream.writeObject(buggybread1);
} catch (Exception e) {
// TODO Auto-generated catch
block
e.printStackTrace();
}
}
}
Q397. Can we compose the Parent
Class object like this ?
class BuggyBread1 extends
BuggyBread2 {
private BuggyBread2 buggybread2;
public static void main(String[]
args){
buggybread2 = new BuggyBread2();
}
}
Q398. Will this code Work ? If
not , Why ?
java.util.Calendar c = new java.util.Calendar();
Q399. Is java.util.Date an
abstract Class ? Is java.util.Calendar an abstract Class ?
Q400. What will the following
code print ?
java.util.Calendar c =
java.util.Calendar.getInstance();
c.add(Calendar.MONTH, 5);
System.out.println(c.getTime());
Q401. Which of the following
code is correct ?
a. DateFormat df =
DateFormat.getInstance();
b. DateFormat df =
DateFormat.getDateInstance();
c. DateFormat df =
DateFormat.getInstance(DateFormat.FULL);
d. DateFormat df =
DateFormat.getDateInstance(DateFormat.FULL);
Q402. What is the use of parse
method in DateFormat ?
Q403. Which of the following is
not a valid java.util.Locale initialization ?
a. new Locale ()
b. new Locale ( String language
)
c. new Locale ( String language
, String country )
Q404. Which of the following is
not a valid NumberFormat initialization ?
a. NumberFormat.getInstance()
b.
NumberFormat.getDateInstance()
c. NumberFormat.getCurrencyInstance()
d. NumberFormat.getNumberInstance()
Q405. What will the following
code print ?
public static void main(String[]
args){
Integer i1 = new
Integer("1");
Integer i2 = new
Integer("2");
Integer i3 =
Integer.valueOf("3");
int i4 = i1 + i2 + i3;
System.out.println(i4);
}
Q406. Which of the following
syntax are correct ?
a. LinkedList l=new
LinkedList();
b. List l=new LinkedList();
c. LinkedList l=new
LinkedList();
d. List l = new LinkedList();
Q407. Which of the following
code is correct ?
a. Date date =
DateFormat.newInstance(DateFormat.LONG, Locale.US).parse(str);
b. Date date =
DateFormat.newInstance(DateFormat.LONG, Locale.US).format(str);
c. Date date =
DateFormat.getDateInstance(DateFormat.LONG, Locale.US).parse(str);
Q408. What's wrong with this
code ?
public static void main(String[]
args) {
String regex =
"(\\w+)*";
String s = "Java is a
programming language.";
Pattern pattern =
Pattern.compile(regex);
Matcher matcher =
pattern.matcher(s);
while (matcher.next()) {
System.out.println("The
e-mail id is: " + matcher.group());
}
}
Q409. Which methods of the
Pattern class have equivalent methods in the String class?
Q410. Can we compare Integers by
using equals() in Java ?
Q411. What is comparator interface
used for ?
Q412. Which are the sorted
collections ?
Q413. What is rule regarding
overriding equals and hasCode method ?
Q414. What is the difference
between Collection and Collections ?
Q415. Is Java a statically typed
or dynamically typed language ?
Q416. What do you mean by
"Java is a statically typed language" ?
Q417. How can we reverse the order
in the TreeMap ?
Q418. TreeMap orders the elements
on which field ?
Q419. How TreeMap orders the
elements if the Key is a String ?
Q420. Can we add heterogeneous
elements into TreeMap ?
Q421. Will it create any problem
if We add elements with key as user defined object into the TreeMap ?
Q422. Can we null keys in
TreeMap ?
Q423. Can value be null in
TreeMap ?
Q424. Which interface TreeMap
implements ?
Q425. Do we have form beans in
Struts 2 ?
Q426. What is a
ConcurrentHashMap ?
Q427. What is the use of double
checked locking in createInstance() of Singleton class?
Double checked locking code:
public static Singleton
createInstance() {
if(singleton == null){
synchronized(Singleton.class) {
if(singleton == null) {
singleton = new Singleton();
}
}
}
return singleton;}
Single checked locking code:
public static Singleton
createInstance() {
synchronized(Singleton.class) {
if(singleton == null) {
singleton = new Singleton();
}
}
return singleton;
}
What advantage does the first
code offer compared to the second ?
Q428. Why are Getter and Setter
better than directly changing and retrieving fields ?
Q429. Can we overload main
method in Java ?
Q430. What the Bean scopes provided
by Spring ?
Q431. What are the various Auto
Wiring types in Spring ?
Q432. Difference between first
level and second level cache in hibernate ?
Q433. What are the the methods
to clear cache in Hibernate ?
Q434. What are different types
of second level cache ?
Q435. Can we disable first level
cache ? What should one do if we don't want an object to be cached ?
Q436. How to configure second
level cache in Hibernate ?
Q437. What is Hibernate ?
Q38. What are the advantages of
Hibernate ?
Q439. What are the different
types of inheritance in Hibernate ?
Q440. What is the purpose of
dialect configured in Hibernate configuration file ?
Q441. Please specify in what
sequence the objects of following classes will be created ?
Session , SessionFactory, Query
, Configuration
Q442. What are different types
of associations in Hibernate ?
Q443. What are the configuration
files in Hibernate ?
Q444. What are the contents of
Hibernate configuration file ( hibernate.cfg.xml ) ?
Q445. What are the Core
Interfaces of Hibernate Framework ?
Q446. What are collection types
in Hibernate ?
Q447. Difference between load
and get ?
Q448. What is lazy fetching in
Hibernate ?
Q449. Different types of Hibernate
Instance States ?
Q450. Is It Good to use
Reflection in an application ? Why ?
Q451. Why is Reflection slower ?
Q452. When should we use
prototype scope and singleton scope for beans ?
Q453. Difference between Assert
and Verify ?
Q454. What is the difference
between ArrayList and LinkedList ?
Q455. Which class elements are
not persisted ?
Q456. Which annotations are used
in Hibernate ?
Q457. What entries we make in
the hibernate config file if we are not using hbm files but Annotations ?
Q458. How many SessionFactory
and Session objects are created ?
Q459. What is the way to
rollback transaction if something goes wrong using hibernate API ?
Q460. What is the use of hbm2ddl
Configuration in Hibernate ?
Q461. What is the difference
between these 2 annotations ?
@Entity
@Entity (
name="EMPLOYEES" )
Q462. "What is the
difference between these 2 annotations ?
@Entity ( name
="EMPLOYEES")
@Entity
@Table (
name=""EMPLOYEES"" )
@Entity ( name="EMP")
@Table (
name="EMPLPYEES" )
Q463. What are the different ID
generating strategies using @GeneratedValue annotation ?
Q464. How to do Eager loading in
Hibernate ?
Q465. What is Lazy Initialization
in Hibernate ?
Q466. What are the ways to avoid
LazyInitializationException ?
Q467. What is cascade ?
Q468. What are the different
Cascade types ?
Q469. Which type of associated
Entities are Eagerly loaded by Default ?
Q470. After which Hibernate
version , related Entities are initialized lazily ?
Q471. Can we declare Entity
class as final ?
Q472. What are the restrictions
for the entity classes ?
Q473. What is the difference
between int[] x; and int x[]; ?
Q474. What are the annotations
used in Junit with Junit4 ?
Q475. What is asynchronous I/O ?
Q476. If there is a conflict
between Base Class Method definition and Interface Default method definition,
Which definition is Picked ?
Q477. What are new features introduced
with Java 8 ?
Q478. Can we have a default
method without a Body ?
Q479. Does java allow
implementation of multiple interfaces having Default methods with Same name and
Signature ?
Q480. What are Default Methods ?
Q481. Can we have a default
method definition in the interface without specifying the keyword
"default" ?
Q482. Can a class implement two
Interfaces having default method with same name and signature ?
public interface
DefaultMethodInterface {
default public void
defaultMethod(){
System.out.println("DefaultMethodInterface");
}
}
public interface
DefaultMethodInterface2 {
default public void
defaultMethod(){
System.out.println("DefaultMethodInterface2");
}
}
public class HelloJava8
implements DefaultMethodInterface,DefaultMethodInterface2 {
public static void main(String[]
args){
DefaultMethodInterface defMethIn
= new HelloJava8();
defMethIn.defaultMethod();
}
}
Q483. What If we make the method
as abstract in another Interface ?
public interface
DefaultMethodInterface {
default public void
defaultMethod(){
System.out.println("DefaultMethodInterface");
}
}
public interface
DefaultMethodInterface2 {
public void defaultMethod(){
System.out.println("DefaultMethodInterface2");
}
}
public class HelloJava8
implements DefaultMethodInterface,DefaultMethodInterface2 {
public static void main(String[]
args){
DefaultMethodInterface defMethIn
= new HelloJava8();
defMethIn.defaultMethod();
}
}
Q484. What if we override the
conflicting method in the Class ?
public interface DefaultMethodInterface
{
default public void
defaultMethod(){
System.out.println("DefaultMethodInterface");
}
}
public interface
DefaultMethodInterface2 {
default public void
defaultMethod(){
System.out.println("DefaultMethodInterface2");
}
}
public class HelloJava8
implements DefaultMethodInterface,DefaultMethodInterface2 {
public static void main(String[]
args){
DefaultMethodInterface defMethIn
= new HelloJava8();
defMethIn.defaultMethod();
}
public void defaultMethod(){
System.out.println("HelloJava8");
}
}
Q485. What will happen if there
is a default method conflict as mentioned above and we have specified the same
signature method in the base class instead of overriding in the existing class
?
Q486. If a method definition has
been specified in Class , its Base Class , and the interface which the class is
implementing, Which definition will be picked if we try to access it using
Interface Reference and Class object ?
Q487. If a method definition has
been specified in the Base Class and the interface which the class is
implementing, Which definition will be picked if we try to access it using
Interface Reference and Class object ?
Q488. Can we use static method
definitions in Interfaces ?
Q489. Can we access Interface
static method using Interface references ?
Q490. Can we have default method
with same name and signature in the derived Interface as the static method in
base Interface and vice versa ?
Q491. What is a Lambda
Expression ? What's its use ?
Q492. Difference between
Predicate, Supplier and Consumer ?
Q493. What does the following
lambda expression means ?
helloJava8 ( x-> x%2 )
Q494. What is the difference
between namenode and datanode in Hadoop?
Q495. Write a program to see if
the number is prefect number or not ?
Q496. Difference between a Pointer
and a Reference ?
Q497. Difference between TCP and
UDP ?
Q498. What things you would care
about to improve the performance of Application if its identified that its DB
communication that needs to be improved ?
Q499. Explain Singleton Design
Pattern ?
1. Java OOPS Concepts ?
Ans. Abstraction , Encapsulation
, Inheritance and Polymorphism.
2. Difference between Abstract
and Concrete Class ?
Ans. Abstract classes are only
meant to be sub classed and not meant to be instantiated whereas concrete
classes are meant to be instantiated.
3. Difference between
Overloading and Overriding ?
Ans.
Overloading - Similar Signature
but different definition , like function overloading.
Overriding - Overriding the
Definition of base class in the derived class.
4. Types of Inner classes ?
Ans. Simple Inner Class, Local
Inner Class, Anonymous Inner Class , Static Nested Inner Class.
5. Difference between TreeMap
and HashMap ?
Ans. They are different the way
they are stored in memory. TreeMap stores the Keys in order whereas HashMap
stores the key value pairs randomly.
6. Difference between List ,
Sets and Maps ?
Ans. Lists - Members are stored
in sequence in memory and can be accessed through index. Sets - There is no
relevance of sequence and index. Sets doesn't contain duplicates whereas
multiset can have duplicates. Maps - Contains Key , Value pairs.
7. Difference between Private ,
Public and Protected ?
Ans. Private - Not accessible
outside object scope. Public - Accessible from anywhere. Protected - Accessible
from anywhere within same package.
8. What is role of
Synchronization in Java ?
Ans. Managing exclusive access
of the code block to single thread at a time to maintain its integrity.
9. What is Default Access ?
Ans. Accessible only by the
objects in the same package.
10. Difference between Vector
and ArrayList ?
Ans. Vectors are synchronized
whereas Array lists are not.
11. Difference between class and
objects ?
Ans. Class is a template using
which objects are created in memory.
12. Describe Garbage Collection
in Java ?
Ans. Mechanism by which Java
reclaims the memory inaccessible by the application.
13. What are the types of
Polymorphism in Java ?
Ans. Static ( function
overloading ) and Run time ( Virtual functions )
14. Different ways of using
threads ?
Ans. Extending Thread class and
implementing runnable interface.
15. Difference between
Composition and Inheritence ?
Ans. Has a relationship vs Is a
relationship.
16. What are Static variables ?
Ans. Correspond to class and not
objects. All objects share that variable.
17. Difference between
Interfaces and Abstract classes ?
Ans. Abstract classes have a
body ( member elements ) where as Interfaces just have methods and static
member declarations.
18. Explain Constructor ?
Ans. Its an operation that
initializes the object.
19. What is Dynamic Binding ?
Ans. Association of function
call to function definition during run time.
20. What is the use of Volatile
Keyword ?
Ans. Volatile is a declaration
that a variable can be accessed by multiple threads and hence shouldn't be
cached
21. Explain Serialization ?
Ans. Storing the state of an
object in a file or other medium.
22. What is the use of Transient
Keyword ?
Ans. keyword in Java is used to
indicate that a field should not be serialized.
23. What are Static Methods ?
Ans. Can only operates on static
variables.
25. What is a Final variable ?
Ans. Variable constant. Variable
value can't be changed after instantiation.
26. What is a Final Method ?
Ans. Can't be overridden
27. What is a Final Class ?
Ans. Can't be sub classed.
28 What is an Immutable Object ?
Ans. Object that can't be
changed after instantiation.
29. Difference between checked
and unchecked exceptions ?
Ans. For checked exceptions
compiler throws a errors if they are not checked whereas unchecked exceptions
and caught during runtime only and hence can't be checked.
30 Give an Example of checked
and unchecked exception ?
Ans. ClassNotFoundException is
checked exception whereas NoClassDefFoundError is a unchecked exception.
31. What is a Singleton Class ?
Ans. Using which only 1 object
can be created.
32. Name few Java exceptions ?
Ans. IndexOutofBound ,
NoClassDefFound , OutOfMemory , IllegalArgument.
33. Name few Design Patterns
used for designing Java applications ?
Ans. Singleton , Factory ,
Abstract Factory , Proxy , Command , Builder.
34. Give an example of Runtime
Polymorphism ?
Ans. Action Mapping in a web
application , Generics.
35. Which of the following is
tightly bound ? Inheritance or Composition ?
Ans. Inheritence.
36. Give an Example of Generics
in Java 5 ?
Ans. List<number> aList =
new ArrayList <number>
37. How can we make sure that a
code segment gets executed even in case of uncatched exceptions ?
Ans. By putting it within
finally.
38. Can a class extend an
interface ?
Ans. No Class implement the
interface. An interface can extend another interface.
39. Does Java support multiple
inheritence ?
Ans. No. We can't extend
multiple classes but can implement multiple interfaces.\
40. Can we use an interface
reference for referring to an object ?
Ans Yes we can do it for object
implementing that interface.
41. What do you mean by return
type Void ?
Ans. Returns Nothing.
42. Is Java Compiled or an
Interpreted language ?
Ans Both
43. What is a class file ?
Ans. Compiled Java files.
44. Why Java is a called a platform
independent language ?
Ans. Java creates the pre
compiled files ( class files ) which can then be interpreted on multiple
platforms.
45. Explain the use of
"Native" keyword ?
Ans. Used in method declarations
to specify that the method is not implemented in the same Java source file, but
rather in another language
46. What is "super"
used for ?
Ans. Used to access members of
the base class.
47. What is "this"
keyword used for ?
Ans. Used to represent an
instance of the class in which it appears.
48. What is the default value of
local variable ?
Ans. The local variables are not
initialized to any default value.
49. What will happen if we
declare a class abstract as well as final ?
Ans. Compile time error.
50 Encapsulation ?
Ans. Encapsulation is the
mechanism that binds together code and data it manipulates and keeps both safe
from outside interference and misuse
Subscribe to Java News and
Posts.
Get latest updates and posts on
Java from Buggybread.com
Enter your email address
Delivered by FeedBurner
51. Explain Inheritence ?
Ans. Inheritance is the process
by which one object acquires the properties of another object.
52. Explain Polymorphism ?
Ans. Polymorphism is the feature
that allows one interface to be used for general class actions
53. Difference between assignment
and initialization ?
Ans. Assignment can be done
anytime but initialization can be done only once during object instantiation.
54. Difference between boolean
and Boolean ?
Ans. boolean is a primitive type
whereas Boolean is a class.
55. What is an Immutable object
?
Ans. Objects that can't be
changed after initialization.
56. Give an example of immutable
class ?
Ans. String
57. What is Casting ?
Ans. Process to convert one data
type to another.
58. Explain Finalize () ?
Ans. finalize() method is used
just before an object is destroyed.
59. What are Marker Interfaces ?
Ans. These are the interfaces
which have no declared methods.
60. Name few Java marker
interfaces ?
Ans. Serializable and cloneable.
61. Is runnable a Marker
interface ?
Ans. No , it has run method
declared.
62. Difference between String
and StringBuffer ?
Ans. String is an immutable
class where StringBuffer is not.
63. Difference between Process
and Thread ?
Ans. Process is a program in
execution whereas thread is a separate path of execution in a program.
64. Explain Thread states ?
Ans. ready, running, waiting and
dead.
65. What is a Deadlock ?
Ans. When two threads are
waiting each other and can’t precede the program is said to be deadlock.
66. Difference between Serialization
and Deserialization ?
Ans. Serialization is the
process of writing the state of an object to a byte stream. Deserialization is
the process of restoring these objects.
67. Difference between Java 1.4
and Java 5 ?
Ans. Generics , Autoboxing ,
Enum and Static Imports.
68. Explain Autoboxing ?
Ans. Autoboxing is the automatic
conversion that the Java compiler makes between the primitive types and their
corresponding object wrapper classes
69. What is an Enum type ?
Ans. An enum type is a special
data type that enables for a variable to be a set of predefined constants
70. What are Wrapper Classes ?
Ans. A wrapper class is any
class which "wraps" or "encapsulates" the functionality of
another class or component.
71. What are Primitive Wrapper
Classes ?
Ans. A Wrapper Class that wraps
or encapsulates the primitive data type.
72. Wat is automatic conversion
of primitive data type to its Wrapper class called ?
Ans. Autoboxing.
73. What Design pattern Wrapper
Classes implement ?
Ans. Adapter.
74. What is "Import"
used for ?
Ans. Enables the programmer to
abbreviate the names of classes defined in a package.
75. Explain Servlet Chaining ?
Ans. Servlet chaining is a
technique in which two or more servlets can cooperate in servicing a single
request.
76. What is the difference
between set and list?
Ans. Set stores elements in an
unordered way but does not contain duplicate elements, whereas list stores
elements in an ordered way but may contain duplicate elements. List can also
holds null elements while Set can't.
77. Difference between HashMap
and HashTable ?
Ans. The HashMap class is
roughly equivalent to Hashtable, except that it is unsynchronized and permits
nulls.
78. What is an Iterator ?
Ans. Some of the collection
classes provide traversal of their contents via a java.util.Iterator interface.
This interface allows you to walk through a collection of objects, operating on
each object in turn.
79. What is JVM ?
Ans. Java Virtual Machine or JVM
is an abstract which provides the runtime environment for the Java byte code to
run.
80. What is JDK ?
Ans. Java Development Kit or JDK
is physical entity that comprises of JRE and Development Tools.
81. What is JRE ?
Ans. Java Run Time Environment
is the implementation of JVM.
82. Different types of memory
used by JVM ?
Ans. Class , Heap , Stack ,
Register , Native Method Stack.
83. What is a Class Loader ?
Ans. Part of JVM which is used
to load classes and interfaces.
84. Does Static Public Void
instead of Public static Void gives compilation error ?Ans. No
85. Does constructor returns any
value ?
Ans. Yes , the current instance
or object of the class.
86. Can we make constructor
final ?Ans. No
87. Why main method is static ?
Ans. Object needs to be created for
calling non static methods.
88. What is a Static Block ?
Ans. It is executed before main
method at the time of class loading.
89. Can we execute program
without mail method ?
Ans. Yes , one way is through
static block.
90. What is Cloning ?
Ans. Keyword to create the exact
copy of the object.
91. Can we overload main method
?Ans. Yes.
92. Can we declare main method
as final ?Ans. Yes.
93. What is Static binding ?
Ans. Associating function call
and its definition during compile time.
94. What is Dynamic Binding ?
Ans. Associating function call
and its definition during runtime.
95. Can we declare an interface
method static ?Ans. No
96. Can an interface be final ?Ans.
No
97. Can we declare interface
methods as private ?Ans. No, they are implicitely public.
98. What is a Static import ?
Ans. By static import , we can
access the static members of a class directly without prefixing it with the
class name.
99. Base class for Error and
Exceptions ?Ans. Throwable
100. Difference between
StringBuffer and StringBuilder ?
Subscribe to Java News and
Posts.
Get latest updates and posts on
Java from Buggybread.com
Enter your email address:
Delivered by FeedBurner
Ans. StringBuffer is
synchronized whereas String Builder is not.
101. Default Package for
Collection classes ?Ans. Java.Util
102. Difference between List and
Queue ?
Ans. In queue access can only
happen at the ends whereas we can access any element of the list.
103. Difference between Vector
and ArrayList ?
Ans. Vectors are synchronized
whereas ArrayList are not.
104. Which is the base interface
for all collection classes ?
Ans. Collection interface.
105. How can we make HashMap
synchronized ?
Ans. Map m = Collections.synchronizedMap(hashMap);
106. Difference between Map and HashMap
?
Ans. Map is an interface where
HashMap is the concrete class.
107. Property Class ?
Ans. The properties class is a
subclass of Hashtable that can be read from or written to a stream.
108 Why Java is a preferred technology
for Web Applications ?
Ans. Web application involves
dealing with multiple requests and thread and hence deals with lot of memory
allocation and de allocation. Hence Java with its intrinsic capability of
Garbage collection offer a perfect platform.
109. What are concepts introduced
with Java 5 ?
Ans. Generics , Enums ,
Autoboxing , Annotations and Static Import.
110. Difference between get and
post ?
Ans. Request parameters in get
are passed within url whereas with post these are passed within post body as
object.
111. Difference between C++ and
Java ?
Ans. We have pointers in C++ ,
We have garbage collection in Java.
112. Name few Design Patterns ?
Ans. Singleton , Adapter ,
Factory , Abstract Factory , Builder , Facade , Observer , Proxy , Prototype.
113. Give an Example of Factory
Design Pattern ?
Ans. Action Mapping within Web
Application.
114. Give an example of Adapter
design pattern ?
Ans. Wrapper Classes.
115. Can we override static
methods ?Ans. No
116. What precaution should be
used while dealing with static variables ?
Ans. Static variables are shared
by all objects of the class and hence each instance may update it with its
local value.
117. Can we override main method
?Ans. No
118. Difference between server
side and client side validation ?
Ans. Client side validation is
done using scripting technologies like javascript before the form is submitted
to server whereas server side validation is done after the form is submitted to
server.
119. Difference between sleep
and wait ?
Ans. Sleep puts thread aside for
exactly the time specified. Wait causes a wait of up to time specified. A
thread could stop waiting earlier if it receives the notify() or notifyAll()
call.
120. Name Wrapper classes
available for primitive types ?
Ans.
boolean - java.lang.Boolean
byte - java.lang.Byte
char - java.lang.Character
double - java.lang.Double
float - java.lang.Float
int - java.lang.Integer
long - java.lang.Long
short - java.lang.Short
void - java.lang.Void
121. Explain System.out.println
?
Ans. System is the class having
static variable out that defaults to system console and println is the
overloaded method.
122. Explain public static void
main() ?
Ans. public means it has public
access, static means that the method can be invoked without instantiating the
object, void means it returns nothing.
123. What is Java Byte Code ?
Ans. Java bytecode is the form
of instructions that the Java virtual machine executes.
124. What is the relation
between class file and byte code ?
Ans. Class files holds the
instructions in byte code.
125. How can we make the object
immutable ?
Ans. By making it a final class
and making all members as private with those being initialized through
constructor.
126. What is the purpose of
making an object immutable ?
Ans. Since they cannot change
state, they cannot be corrupted by thread interference or observed in an
inconsistent state.
127. Explain the scenerios to
choose between String , StringBuilder and StringBuffer ?
Ans.
If the Object value will not change in a
scenario use String Class because a String object is immutable.
If the Object value can change and will
only be modified from a single thread, use a StringBuilder because
StringBuilder is unsynchronized(means faster).
If the Object value may change, and can be
modified by multiple threads, use a StringBuffer because StringBuffer is thread
safe(synchronized).
128. Explain
java.lang.OutOfMemoryError ?
Ans. This Error is thrown when
the Java Virtual Machine cannot allocate an object because it is out of memory,
and no more memory could be made available by the garbage collector.
129. Difference between
arraylist and linkedlist ?
Ans. Array list maintains
indices like array whereas Linked List maintain pointers to the next element.
130. Difference between
hashtable and hashmap ?
Ans. Hashtable are synchronized
whereas hashmaps are not. Hashtable doesn't allow null values whereas HashMaps
allows null values.
131. Can we have multiple
servlets in a web application and How can we do that ?
Ans. Yes by making entries in
web.xml
132. Are static members
serialized ?
Ans. Static members don't belong
to a object and hence are not serialized.
133. How can we manage Error
Messages in the web application ?
Ans. Within message.properties
file.
134. What is the use of Marker
interface if they don't hold anything ?
Ans. As the name suggest , They
just mark a class and just indicate something to compiler and JVM.
135. Is JVM, a compiler or
interpretor ?Ans. Its an interpretor.
136. Is Synchronization an
overhead ?
Ans. Synchronization has
relevance only if a code segment can be accessed by multiple threads and hence
may result in ambiguity. Yes Its an overhead if simultaneous access doesn't
pose any problem.
137. Difference between implicit
and explicit type casting ?
Ans. An explicit conversion is
where you use some syntax to tell the program to do a conversion whereas in
case of implicit type casting you need not provide the data type.
138. Can we have an abstract
class without abstract methods ?Ans. Yes
139. Can we have abstract
methods in a class which is not Abstract ?Ans. No
140. Are list , Map and Set
Classes or Interfaces ? Ans. These are interfaces.
141. Difference between .equals
and == ?
Ans. .equals is the method of
object class and is used to match the content of object whereas == matches the
objects itself. So == looks to see if they are same object.
142. What are the methods of
Object class ?
Ans. toString , clone , finalize
, hashcode , equals.
143. What are the class loaders
?
Ans. JVM loads the classes
through class loaders.
144. What are the different
class loaders used by JVM ? Ans. Bootstrap , Extension and System.
145. difference between
loadClass and Class.forName ?
Ans. loadClass only loads the
class but doesn't initialize the object whereas Class.forName initialize the
object after loading it.
146. How do we load the DB
drivers ?Ans. Using Class.forName
147. Have you ever destroyed
objects yourself ?
Ans. Java by its mechanism of
Garbage collection does this itself.
148. Should we override finalize
method ?
Ans. Finalize is used by Java
for Garbage collection. It should not be done as we should leave the Garbage
Collection to Java itself.
149. Will finally be executed
for handled or unhandled exceptions ?
Ans. Both.
150. Difference between
protected and default Modifier ?
Ans. With protected member is
accessible in subclass whereas with Default Member is not accessible in
subclass.
151. Can we overload methods on
a single parameter with data types as int and long. For example - int
calculate(int x) and int calculate(long x)
?Ans. Yes
152. What will happen if we call
such method using a number lets say calculate(5) ?
Ans. It will call first method
with int argument.
153. Then whats the use of
second method. Will that ever be called ?
Ans. we can call by having
argument as 5L.
154. What is servlet Chaining ?
Ans. Multiple servlets serving
the request in chain.
155. In the following code
String str1 = new
String("abc");
String str2 = new String("abc");
Which of the following will be
true.
str == str2
str.equal(str2)
Ans. str.equal(str2) will be
true but str==str2 will be false
156. In the following code
String str1 = new
String("abc");
String str2 = new
String("xyz");
str1=str2;
Which of the following will be
true.
str == str2
str.equal(str2)
Ans. both str.equal(str2) and
str==str2 will be true
157. What is keyword instanceOf
used for ?
Ans. It is used to see if an object is an instance
of a specific class.
158. If we obj is an object of
Class A and Class A extends Class B , What will obj instanceof B will return ?
Ans. True
159. What is assert keyword used
for ?
Ans. The assert keyword is used
to make an assertion—a statement which the programmer believes is always true
at that point in the program. This keyword is intended to aid in testing and
debugging.
160. Any example of Serialization
in your application ?
Ans. Properties Class.
161. Difference between Factory
and Abstract Factory Design Pattern ?
Ans. Factory Pattern deals with
creation of objects delegated to a separate factory class whereas Abstract
Factory patterns works around a super-factory which creates other factories.
162. Difference between Factory
and Builder Design Pattern ?
Ans. Builder pattern is the
extension of Factory pattern wherein the Builder class builds a complex object
in multiple steps.
163. Difference between Proxy
and Adapter ?
Ans. Adapter object has a
different input than the real subject whereas Proxy object has the same input
as the real subject. Proxy object is such that it should be placed as it is in
place of the real subject.
164. Difference between Adapter
and Facade ?
Ans. The Difference between
these patterns in only the intent. Adapter is used because the objects in
current form cannot communicate where as in Facade , though the objects can
communicate , A Facade object is placed between the client and subject to simplify
the interface.
165. Difference between Builder
and Composite ?
Ans. Builder is a creational
Design Pattern whereas Composite is a structural design pattern. Composite
creates Parent - Child relations between your objects while Builder is used to
create group of objects of predefined types.
166. Example of Chain of Responsibility
Design Pattern ?
Ans. Exception Handling Throw
mechanism.
167. Example of Observer Design
Pattern ?
Ans. Listeners.
168. Difference between Factory
and Strategy Design Pattern ?
Ans. Factory is a creational
design pattern whereas Strategy is behavioral design pattern. Factory revolves
around the creation of object at runtime whereas Strategy or Policy revolves around
the decision at runtime.
169. Shall we use abstract
classes or Interfaces in Policy / Strategy Design Pattern ?
Ans. Strategy deals only with
decision making at runtime so Interfaces should be used.
170. Which kind of memory is
used for storing object member variables and function local variables ?
Ans. Local variables are stored
in stack whereas object variables are stored in heap.
171. Why do member variables
have default values whereas local variables don't have any default value ?
Ans. member variable are loaded
into heap, so they are initialized with default values when an instance of a
class is created. In case of local variables, they are stored in stack until
they are being used.
172. What is the default value
for Object Reference in Java ?Ans. Null
173. What is a Default
Constructor ?
Ans. The no argument constructor
provided by Java Compiler if no constructor is specified.
174. Will Compiler creates a
default no argument constructor if we specify only multi argument constructor ?
Ans. No, Compiler will create
default constructor only if we don't specify any constructor.
175. Can we overload constructors ?Ans. Yes.
176. What will happen if we make
the constructor private ?
Ans. We can't create the objects
directly by invoking new operator.
177. How can we create objects
if we make the constructor private ?
Ans. We can do so through a
static public member method.
178. Is that the only way to
initialize the object in that case ?
Ans. We can also do so using
static block.
179. Is constructor inherited ?Ans.
No
180. What will happen if we
remove the static keyword from main method ?
Ans. Program will compile but
will give a "NoSuchMethodError" during runtime.
181. Which is the super class of
all classes in java ?
Ans. Object Class
182. Why Java don't use pointers
?
Ans. Pointers are vulnerable and
slight carelessness in their use may result in memory problems and hence Java intrinsically
manage their use.
183. Can we use both
"this" and "super" in a constructor ?
Ans. No, because both this and
super should be the first statement.
184. Can we achieve runtime
polymorphism by data members ?Ans. No
185. Do we need to import
java.lang.package ?Ans. No, It is loaded by default by the JVM.
186. Can i import same package /
class twice ?
Ans. Compiler doesn't give any
error if we try to import same package or class twice but internally JVM will
load the class only once.
187. Is it necessary that each
try block to be followed by catch block ?Ans. It should be followed by either
catch or finally block.
188. Can finally block be used
without catch ?Ans. Yes but should follow "try" block then.
189. Can an exception be
rethrown ?Ans. Yes
190. What is exception
propogation ?
Ans. Passing the exception
object to the calling method.
191. What is the use of toString
method ?
Ans. It provides the string
representation of an object.
192. Difference between nested
and inner classes ?
Ans. Inner classes are non
static nested classes.
193. What is a nested interface
?
Ans. Any interface declared
inside a class or an interface. It is static by default.
194. Can an unreferenced object
be referenced again ?
Ans. Yes.
195. What kind of thread is
garbage collector thread ?
Ans. Dameon Thread.
196. What is an Externalizable
interface ?
Ans. Externalizable interface is
used to write the state of an object into a byte stream in compressed format.
197. Difference between
serializable and externalizable interface ?
Ans. Serializable is a marker
interface whereas externalizable is not.
198. What is reflection ?
Ans. It is the process of
examining / modifying the runtime behaviour of an object at runtime.
199. What is the purpose of
System Class ?
Ans. To provide access to the
system resources.
200. What is Locale ?
Ans. A Locale object represents
a specific geographical, political, or cultural region.
201. Situations where
"this" keyword can be used ?
Ans.
a. While accessing the member
variable having same name as local variable.
b. constructor chaining
c. pass the current object as a
parameter to another method.
202. Can we declare interface
method's private ?
Ans. No
203. What is the problem with
following code ?
if(x == null && x.getMethod()
== true)
Ans. It will throw NPE in case x
is null.
204. Can we instantiate the
object of derived class if parent constructor is protected ?
Ans. Yes.
206. Can we declare an abstract
method private ?
Ans. No Abstract methods can
only be declared protected or public.
207. Can Abstract methods in
parent class have a body ?Ans. No.
208. Can we declare a class
static ?
Ans. We cab only declare the
inner class as static but not the top level class.
209. Can we reduce the visibility
of the overridden method ?Ans. No.
210. Can we make an object final
i.e immutable using final keyword ?
Ans. No, only object reference
can be made final. This means that the reference cannot be reassigned.
211. What are the design
considerations while making a choice between using interface and abstract class
?
Ans. Keep it as a Abstract Class
if its a "Is a" Relationsship and should do subset/all of the
functionality. Keep it as Interface if its a "Should Do"
relationship.
