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

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Q1111. 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.

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Q1112. 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.

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Q1113. 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.

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Q1114. What is assert keyword used for ?

Ans. The assert keyword is used to make an assertionâ€”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.

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Q1115. Difference between Factory and Abstract Factory Design Pattern ?

Design

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.

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Q1116. Difference between Factory and Builder Design Pattern ?

Design

Ans. Builder pattern is the extension of Factory pattern wherein the Builder class builds a complex object in multiple steps.

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Q1117. Difference between Proxy and Adapter ?

Design

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.

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Q1118. Difference between Adapter and Facade ?

Design

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.

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Q1119. 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.

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Q1120. Example of Chain of Responsibility Design Pattern ?

Ans. Exception Handling Throw mechanism.

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Q1121. Example of Observer Design Pattern ?

Ans. Listeners.

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Q1122. Difference between Factory and Strategy Design Pattern ?

Design

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.

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Q1123. 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.

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Q1124. 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.

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Q1125. Why do member variables have default values whereas local variables don't have any default value ?

Core Java

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.

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Q1126. What is a Default Constructor ?

Core Java

Ans. The no argument constructor provided by Java Compiler if no constructor is specified.

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Q1127. 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.

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Q1128. Can we overload constructors ?

Ans. Yes.

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Q1129. What will happen if we make the constructor private ?

Core Java

Ans. We can't create the objects directly by invoking new operator.

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Q1130. How can we create objects if we make the constructor private ?

Core Java

Ans. We can do so through a static public member method or static block.

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Q1131. 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.

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Q1132. Can we use both "this()" and "super()" in a constructor ?

Core Java

Ans. No, because both this and super should be the first statement.

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Q1133. Do we need to import java.lang package ?

Core Java

Ans. No, It is loaded by default by the JVM.

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Q1134. Is it necessary that each try block to be followed by catch block ?

Core Java

Ans. It should be followed by either catch or finally block.

Sample Code for Retry in case of exception

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Q1135. Can finally block be used without catch ?

Core Java

Ans. Yes but should follow "try" block then.

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Q1136. What is exception propogation ?

Core Java

Ans. Passing the exception object to the calling method.

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Q1137. Difference between nested and inner classes ?

Ans. Inner class is a type of nested class.

Inner classes are non static nested classes i.e the one that are associated with the instance of outer class.

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Q1138. What is a nested interface ?

Ans. Any interface declared inside a class or an interface. It is static by default.

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Q1139. What is an Externalizable interface ?

Ans. Externalizable interface is used to write the state of an object into a byte stream in compressed format.

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Q1140. Difference between serializable and externalizable interface ?

Ans. Serializable is a marker interface whereas externalizable is not.

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