Java Interview Question Answer




Question : 1
What do you know about Java?

Question : 2
What are the supported platform by Java Programming Language?

Question : 3
List any five features of Java?

Question : 4
Why is Java Architectural Neutral?

Question : 5
How Java enabled High Performance?

Question : 6
Why Java is considered dynamic?

Question : 7
What is Java Virtual Machine and how it is considered in context of Java's platform independent feature?

Question : 8
List two Java IDE's?

Question : 9
List some Java keywords(unlike C, C++ keywords)?

Question : 10
What do you mean by Object?

Question : 11
Define class?

Question : 12
What kind of variables a class can consist of?

Question : 13
What is a Local Variable

Question : 14
What is a Instance Variable

Question : 15
What is a Class Variable

Question : 16
What is Singleton class?

Question : 17
What do you mean by Constructor?

Question : 18
List the three steps for creating an Object for a class?

Question : 19
What is the default value of byte datatype in Java?

Question : 20
What is the default value of float and double datatype in Java?

Question : 21
When a byte datatype is used?

Question : 22
What is a static variable?

Question : 23
What do you mean by Access Modifier?

Question : 24
What is protected access modifier?

Question : 25
What do you mean by synchronized Non Access Modifier?

Question : 26
: According to Java Operator precedence, which operator is considered to be with highest precedence?

Question : 27
Variables used in a switch statement can be used with which datatypes?

Question : 28
When parseInt() method can be used?

Question : 29
Why is String class considered immutable?

Question : 30
Why is StringBuffer called mutable?

Question : 31
What is the difference between StringBuffer and StringBuilder class?

Question : 32
Which package is used for pattern matching with regular expressions?

Question : 33
java.util.regex consists of which classes?

Question : 34
What is finalize() method?

Question : 35
What is an Exception?

Question : 36
What do you mean by Checked Exceptions?

Question : 37
What do you mean by Checked Exceptions?

Question : 38
Explain Runtime Exceptions?

Question : 39
Which are the two subclasses under Exception class?

Question : 40
When throws keyword is used?

Question : 41
When throw keyword is used?

Question : 42
How finally used under Exception Handling?

Question : 43
What things should be kept in mind while creating your own exceptions in Java?

Question : 44
Define Inheritance?

Question : 45
When super keyword is used?

Question : 46
What is Polymorphism?

Question : 47
What is Abstraction?

Question : 48
What is Abstract class

Question : 49
When Abstract methods are used?

Question : 50
What is Encapsulation?

Question : 51
What is the primary benefit of Encapsulation?

Question : 52
What is an Interface?

Question : 53
Give some features of Interface?

Question : 54
Define Packages in Java?

Question : 55
Why Packages are used?

Question : 56
What do you mean by Multithreaded program?

Question : 57
What are the two ways in which Thread can be created?

Question : 58
What is an applet?

Question : 59
An applet extend which class?

Question : 60
Explain garbage collection in Java?

Question : 61
Define immutable object?

Question : 62
Explain the usage of this() with constructors?

Question : 63
Explain Set Interface?

Question : 64
Explain TreeSet?

Question : 65
What is Comparable Interface?

Question : 66
Difference between throw and throws?

Question : 67
Explain the following line used under Java Program: public static void main (String args[ ])

Question : 68
Define JRE i.e. Java Runtime Environment?

Question : 69
What is JAR file?

Question : 70
What is a WAR file?

Question : 71
Define JIT compiler?

Question : 72
What is the difference between object oriented programming language and object based programming language?

Question : 73
What is the purpose of default constructor?

Question : 74
Can a constructor be made final?

Question : 75
What is static block?

Question : 76
Define composition?

Question : 77
What is function overloading?

Question : 78
What is function overriding?

Question : 79
Difference between Overloading and Overriding?

Question : 80
What is final class?

Question : 81
What is NullPointerException?

Question : 82
What are the ways in which a thread can enter the waiting state?

Question : 83
How does multi-threading take place on a computer with a single CPU?

Question : 84
What invokes a thread's run() method?

Question : 85
Does it matter in what order catch statements for FileNotFoundException and IOException are written?

Question : 86
What is the difference between yielding and sleeping?

Question : 87
Why Vector class is used?

Question : 88
How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8 characters?

Question : 89
What are Wrapper classes?

Question : 90
What is the difference between a Window and a Frame?

Question : 91
Which package has light weight components?

Question : 92
What is the difference between the paint() and repaint() methods?

Question : 93
What is the purpose of File class?

Question : 94
What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?

Question : 95
Which class should you use to obtain design information about an object?

Question : 96
What is the difference between static and non-static variables?

Question : 97
What is Serialization and deserialization?

Question : 98
What are use cases?

Question : 99
Explain the use of sublass in a Java program?

Question : 100
How to add menushortcut to menu item?

Question : 101
Can you write a Java class that could be used both as an applet as well as an application?

Question : 102
What is the difference between Swing and AWT components?

Question : 103
What's the difference between constructors and other methods?

Question : 104
Is there any limitation of using Inheritance?

Question : 105
When is the ArrayStoreException thrown?

Question : 106
Can you call one constructor from another if a class has multiple constructors?

Question : 107
the difference between the methods sleep() and wait()?

Question : 108
When ArithmeticException is thrown?

Question : 109
What is a transient variable?

Question : 110
What is synchronization?

Question : 111
What is the Collections API?

Question : 112
Does garbage collection guarantee that a program will not run out of memory?

Question : 113
The immediate superclass of the Applet class?

Question : 114
Which Java operator is right associative?

Question : 115
What is the difference between a break statement and a continue statement?

Question : 116
If a variable is declared as private, where may the variable be accessed?

Question : 117
What is the purpose of the System class?

Question : 118
List primitive Java types?

Question : 119
What is the relationship between clipping and repainting under AWT?

Question : 120
Which class is the immediate superclass of the Container class?

Question : 121
What class of exceptions are generated by the Java run-time system?

Question : 122
Under what conditions is an object's finalize() method invoked by the garbage collector?

Question : 123
How can a dead thread be restarted?

Question : 124
Which arithmetic operations can result in the throwing of an ArithmeticException?

Question : 125
Variable of the boolean type is automatically initialized as?

Question : 126
Can try statements be nested?

Question : 127
What are ClassLoaders?

Question : 128
What is the difference between an Interface and an Abstract class?

Question : 129
What will happen if static modifier is removed from the signature of the main method?

Question : 130
What is the default value of an object reference declared as an instance variable?

Question : 131
Can a top level class be private or protected?

Question : 132
Why do we need wrapper classes?

Question : 133
What is the difference between error and an exception?

Question : 134
Is it necessary that each try block must be followed by a catch block?

Question : 135
When a thread is created and started, what is its initial state?

Question : 136
What is the Locale class?

Question : 137
What are synchronized methods and synchronized statements?

Question : 138
What is runtime polymorphism or dynamic method dispatch?

Question : 139
What is Dynamic Binding(late binding)?

Question : 140
Can constructor be inherited?

Question : 141
What are the advantages of ArrayList over arrays?

Question : 142
Why deletion in LinkedList is fast than ArrayList?

Question : 143
How do you decide when to use ArrayList and LinkedList?

Question : 144
What is a Values Collection View ?

Question : 145
What is dot operator?

Question : 146
Where and how can you use a private constructor?

Question : 147
What is type casting?

Question : 148
Describe life cycle of thread?

Question : 149
What is the difference between the >> and >>> operators?

Question : 150
Which method of the Component class is used to set the position and size of a component?

Question : 151
What is the range of the short type?

Question : 152
What is the immediate superclass of Menu?

Question : 153
Does Java allow Default Arguments?

Question : 154
Which number is denoted by leading zero in java?

Question : 155
Which number is denoted by leading 0x or 0X in java?

Question : 156
Break statement can be used as labels in Java?

Question : 157
Where import statement is used in a Java program?

Question : 158
Explain suspend() method under Thread class>

Question : 159
Explain isAlive() method under Thread class?

Question : 160
What is currentThread()?

Question : 161
Explain main thread under Thread class execution?

Question : 162
Life cycle of an applet includes which steps?

Question : 163
Why is the role of init() method under applets?

Question : 164
Which method is called by Applet class to load an image?

Question : 165
Define code as an attribute of Applet?

Question : 166
Define canvas?

Question : 167
Define Network Programming?

Question : 168
What is a Socket?

Question : 169
Advantages of Java Sockets?

Question : 170
Disadvantages of Java Sockets?

Question : 171
Which class is used by server applications to obtain a port and listen for client requests?

Question : 172
Which class represents the socket that both the client and server use to communicate with each other?

Question : 173
Why Generics are used in Java?

Question : 174
What environment variables do I need to set on my machine in order to be able to run Java programs?

Question : 175
Is there any need to import java.lang package?

Question : 176
What is Nested top-level class?

Question : 177
What is Externalizable interface?

Question : 178
If System.exit (0); is written at the end of the try block, will the finally block still execute?

Question : 179
What is daemon thread?

Question : 180
Which method is used to create the daemon thread?

Question : 181
Which method must be implemented by all threads?

Question : 182
What is the GregorianCalendar class?

Question : 183
What is the SimpleTimeZone class?

Question : 184
What is the difference between the size and capacity of a Vector?

Question : 185
Can a vector contain heterogenous objects?

Question : 186
What is an enumeration?

Question : 187
What is difference between Path and Classpath?

Question : 188
Can a class declared as private be accessed outside it's package?

Question : 189
What are the restriction imposed on a static method or a static block of code?

Question : 190
Can an Interface extend another Interface?

Question : 191
Which object oriented Concept is achieved by using overloading and overriding?

Question : 192
What is an object's lock and which object's have locks?

Question : 193
What is Downcasting?

Question : 194
What are order of precedence and associativity and how are they used?

Question : 195
If a method is declared as protected, where may the method be accessed?

Question : 196
What is the difference between inner class and nested class?

Question : 197
What restrictions are placed on method overriding?

Question : 198
What is constructor chaining and how is it achieved in Java?

Question : 199
Can a double value be cast to a byte?

Question : 200
How does a try statement determine which catch clause should be used to handle an exception?

Question : 201
What will be the default values of all the elements of an array defined as an instance variable?

Question : 202
What is the difference between an Interface and an Abstract class?

Question : 203
What is the purpose of garbage collection in Java, and when is it used?

Question : 204
Describe synchronization in respect to multithreading.

Question : 205
Explain different way of using thread?

Question : 206
What is JDK?

Question : 207
What is the significance of the .class file?

Question : 208
How many classes can be declared in a Java program?

Question : 209
How is the main() method invoked?

Question : 210
How many classes can contain the main() method in a Java program?

Question : 211
What is the out object?

Question : 212
Why do you need to put an f' literal after a floating point constant?

Question : 213
Does Java support multiple inheritance?

Question : 214
Can I instantiate an interface?

Question : 215
What is the return value of the getContentPane()method?

Question : 216
What is the difference between a frame and a dialog box?

Question : 217
Can you write a java code that works both as an applet and an application?

Question : 218
Can I put more than one applet on a Web page?

Question : 219
How do I determine the width and the height of my applet?

Question : 220
Should applets have constructors?

Question : 221
Why do I get RuntimeAccessPermission exception when I am trying to execute a Java program which will load an image?

Question : 222
Why does my program not load the image even when the gif files are present in the specified directory?

Question : 223
When do I need to flush an output stream?

Question : 224
What is the advantage of Buffered streams over normal streams?

Question : 225
How do I read a line of input at a time?

Question : 226
What is meant by Serialization?

Question : 227
Give two examples of real world objects. Also specify their characteristics and behaviour.

Question : 228
What do you understand by state of an object? Explain with an example.

Question : 229
How are objects implemented in Software?

Question : 230
What is abstraction? How is encapsulation related to it?

Question : 231
Define Encapsulation.

Question : 232
Explain the term object using an example.

Question : 233
What is Object Oriented Programming?

Question : 234
Give a real life example of Polymorphism.

Question : 235
What is Java API?

Question : 236
Define the term Byte Code.

Question : 237
What is JVM? Explain its relationship with byte code.

Question : 238
What is a platform? How does it differ from a Java platform?

Question : 239
State the difference between Applet and Application.

Question : 240
What makes Java suitable to create secured applications?

Question : 241
What does the Robust feature in Java mean?

Question : 242
What is Multithreading in Java?

Question : 243
What makes Java Architecture Neutral?

Question : 244
What is WORA?

Question : 245
Explain the statement “Byte code is the object code for the JVM”

Question : 246
State two differences between fundamental and user-defined data type.

Question : 247
State two differences between a class and an object.

Question : 248
Why is a class called a user defined data type?

Question : 249
What is an access specifier? Which two access specifier is used in a class declaration?

Question : 250
Why is a class called an object factory?

Question : 251
State two rules you should follow for naming a class

Question : 252
What two conventions you should follow naming a class?

Question : 253
State two conventions you should follow while naming a class.

Question : 254
How are Decimal, Octal and Hexadecimal integer literals represented in Java?

Question : 255
What are separators?

Question : 256
What is Type Conversion? Name the two type conversions in Java.

Question : 257
What is an operator? How is the classification of operators based upon?

Question : 258
What is an expression?

Question : 259
What is an accumulator?

Question : 260
What is a bug? What is debugging?

Question : 261
What are the different type of errors that may occur in a Java program?

Question : 262
What are syntax errors? Give two examples.

Question : 263
What are run-time errors? Give two examples.

Question : 264
What are comments? Name the different types of comments used in Java.

Question : 265

Give two examples of real world objects. Also specify their characteristics and behaviour.


Question : 266

What is the difference between break and continue statements when they occur in a loop?


Question : 267

State one similarity and one difference between while and for loop.


Question : 268

Name two jump statements and their use


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