Interview Questions and Answers for 'Java' | Search Interview Question

Interview Questions and Answers - Order By Rating

Q1081. Give an Example of checked and unchecked exception ?

Core Java

Ans. ClassNotFoundException is checked exception whereas NoClassDefFoundError is a unchecked exception.

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Q1082. Name few Java Exceptions ?

Core Java

Ans. IndexOutofBoundException ,
NoClassDefFoundException ,
OutOfMemoryException ,
IllegalArgumentException,
NullPointerException,
IllegalStateException

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Frequently asked to fresh graduates and less experienced.

Q1083. Which of the following is tightly bound ? Inheritance or Composition ?

Core Java

Ans. Inheritance.

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Q1084. How can we make sure that a code segment gets executed even in case of uncatched exceptions ?

Ans. By putting it within finally.

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Q1085. Explain the use of "Native" keyword ?

Core Java

Ans. Used in method declarations to specify that the method is not implemented in the same Java source file, but rather in another language

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Q1086. What is "super" used for ?

Ans. Used to access members of the base class.

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Q1087. What is "this" keyword used for ?

Ans. Used to represent an instance of the class in which it appears.

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Q1088. Difference between boolean and Boolean ?

Core Java

Ans. boolean is a primitive type whereas Boolean is a class.

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Q1089. What is a finalize method ?

Core Java

Ans. finalize() method is called just before an object is destroyed.

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Very frequently asked in phone and walk in interviews.

Q1090. What are Marker Interfaces ? Name few Java marker interfaces ?

Core Java

Ans. An interface without any method declaration is called as marker interface. there are 3 in-built interfaces in JVM i.e. serializable, clonable, remote

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Q1091. Is runnable a Marker interface ?

Core Java

Ans. No , it has run method declared.

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Frequently asked to fresh graduates.

Q1092. Difference between Process and Thread ?

Operating System

Ans. Process is a program in execution whereas thread is a separate path of execution in a program.

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Q1093. What is a Deadlock ?

Operating System

Ans. When two threads are waiting each other and cant precede the program is said to be deadlock.

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Q1094. Difference between Serialization and Deserialization ?

Core Java

Ans. Serialization is the process of writing the state of an object to a byte stream. Deserialization is the process of restoring these objects.

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Q1095. Explain Autoboxing ?

Core Java

Ans. Autoboxing is the automatic conversion that the Java compiler makes between the primitive types and their corresponding object wrapper classes

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Q1096. What is an Enum type ?

Core Java

Ans. An enum type is a special data type that enables for a variable to be a set of predefined constants

Sample Code for enum

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Q1097. What are Wrapper Classes ? What are Primitive Wrapper Classes ?

Core Java

Ans. A wrapper class is any class which "wraps" or "encapsulates" the functionality of another class or component. A Wrapper Class that wraps or encapsulates the primitive data type is called Primitive Wrapper Class.

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Q1098. What Design pattern Wrapper Classes implement ?

Design

Ans. Adapter.

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Q1099. What is "Import" used for ?

Core Java

Ans. Enables the programmer to abbreviate the names of classes defined in a package.

Sample Code for import

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Q1100. Different types of memory used by JVM ?

Core Java

Ans. Class , Heap , Stack , Register , Native Method Stack.

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Q1101. What is a class loader ? What are the different class loaders used by JVM ?

Core Java

Ans. Part of JVM which is used to load classes and interfaces.

Bootstrap , Extension and System are the class loaders used by JVM.

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Q1102. Can we declare interface methods as private ?

Ans. With Java 9 we can declare interface methods as private

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Q1103. What is a Static import ?

Core Java

Ans. By static import , we can access the static members of a class directly without prefixing it with the class name.

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Very frequently asked. Usually difference between String,StringBuffer and StringBuilder is asked in different variations.

Q1104. Difference between StringBuffer and StringBuilder ?

Core Java

Ans. StringBuffer is synchronized whereas StringBuilder is not.

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Q1105. Difference between Map and HashMap ?

Core Java

Ans. Map is an interface where HashMap is the concrete class.

Sample Code for map

Sample Code for hashmap

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Q1106. What is a Property class ?

Core Java

Ans. The properties class is a subclass of Hashtable that can be read from or written to a stream.

Sample Code for Load Properties using Property Class

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Very frequently asked in different variations. Frequently asked in Deloitte ( 2 feedback ) , HCL Tech ( 3 feedback ), TCS and Coginizant (CTS)

Q1107. Explain the scenerios to choose between String , StringBuilder and StringBuffer ?

or

What is the difference between String , StringBuilder and StringBuffer ?

Core Java

Ans. If the Object value will not change, 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 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).

Sample Code for String

Sample Code for StringBuffer

Sample Code for StringBuilder

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Q1108. Explain java.lang.OutOfMemoryError ?

Core Java

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.

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Q1109. Can we have multiple servlets in a web application and How can we do that ?

Java EE

Ans. Yes by making entries in web.xml

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Frequently asked to fresh graduates.

Q1110. Is JVM, a compiler or interpretor ?

Ans. Its an interpretor.

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