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

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Q661. Can we use java keywords as identifiers ?

Core Java

Ans. No, keyword has pre defined meaning for compiler and hence cannot be used as identifiers.

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Q662. What is a difference between Identifier and keyword ?

Core Java

Ans. Keyword is a reserved word that has a pre defined meaning for the compiler and hence cannot be used as an identifier, for example - final, private , for etc.

Identifier is the name given by the programmer to a programming construct, for example - class and method names etc.

java Keywords cannot be used as an identifier in java.

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Q663. Which of the following applies to "private"?

It is a keyword
It is a modifier
It is an access modifier

Core Java

Ans. Yes, all of them applies to private keyword. It is an access modifier.

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Q664. Which of the following applies to Final ?

It is a keyword
It is a modifier
It is an access modifier

Core Java

Ans. It is a keyword and a modifier but not an access modifier.

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Q665. What is the difference between a keyword and a modifier ?

Core Java

Ans. Keywords are the reserved words that have a pre defined meaning for a compiler whereas modifiers are the type of keywords that modifies the state or definition of a programming construct.

for, while are keywords but not modifiers.
private , public , final , abstract etc are keywords as well as modifiers.

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Q666. What are access and non access modifiers ?

Core Java

Ans. Access modifiers are the java reserved keywords that changes the access privileges on a class , method , element etc. For example - public , private and protected.

Non Access modifiers are the java modifiers other than access modifiers. For example - static , final, abstract, synchronized, transient, volatile etc.

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Q667. Is synchronized a keyword , modifier, identifier? what is it ?

Core Java

Ans. synchronized is a keyword and a modifier. The synchronized keyword is used to indicate that a method can be accessed exclusively by one thread at a time.

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Q668. In Java, if object A contains same the same data of object B, are they equal?

Core Java

Ans. it depends on the implementation of equals method of the respective class. If no definition is provided and it uses the default definition of the object class, two references are equal only if they point to the same object.

We can have such an equality defined for a particular class objects if we provide appropriate implementation of equals method comparing all those fields.

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Q669. Difference between void and return ? Can we have return statement in the void method ?

Core Java

Ans. void is a declaration that states that the method declared void is not expected to return anything.

return is a statement within the method that returns the control out of the method.

Yes, we can have return statement in the void method but without any argument.

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Q670. Explain OOPS.

Core Java

^{This question was recently asked at 'Acute Informatics,General Atomics'.This question is still unanswered. Can you please provide an answer.}

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Q671. Why do we need polymorphism in Java ?

Core Java

Ans. Frankly saying I dont see much use of method overloading as its just little design convenience as you can use the same name but still have binding to different methods depending on the need.

Method overriding is really important and is much more useful than method overloading. Along with other programming concepts like interfaces and dependency injection , it facilitates the development of software as libraries and plug-gable components.

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Q672. What will happen if we don't have termination statement in recursion ?

Core Java

Ans. It would result in endless function calls and hence eventually would result in stackoverflow exception.

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Q673. What is recursion in Java ?

Core Java

Ans. It's a programming technique wherein the method can call itself. The method call usually involves a different set of parameters as otherwise it would lead to an infinite loop. There is usually a termination check and statement to finally return the control out of all function calls.

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Q674. What are the counter controlled repetitions in java ?

Core Java

Ans. Counter controlled repetitions are the loops that are controlled with the use of counters or the loops where the number of repetitions are known in advance. for loop in java is the counter controlled repetition.

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Q675. What is JVM ?

Core Java

Ans. JVM (Java Virtual Machine) is an abstract machine. It is a specification that provides runtime environment in which java bytecode can be executed.JVMs are available for many hardware and software platforms (i.e. JVM is platform dependent).Runtime Instance Whenever you write java command on the command prompt to run the java class, an instance of JVM is createdThe JVM performs following operation:Loads codeVerifies codeExecutes codeProvides runtime environment

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Q676. What is synchronization ?

Core Java

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Q677. What is the use of constructors in Java ?

Core Java

Ans. Constructors are used to initialize the state of an object. If there are no constructor , objects won't have any initialized state and hence it's elements may contain garbage values. If the memory were used as is, the behavior of the object would also be unpredictable.

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Q678. What will we get if we try to print local variable that hasn't been initialized ?

Core Java

Ans. It will print the garbage value as compiler doesn't provide a default value to local variables.

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Q679. If we don't provide any argument to the executed program, What arguments will be passed to the main method ? Will the String array argument be null ?

Core Java

Ans. No. It won't be null but an empty array with size 0

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Q680. Why can't we create an instance of abstract class ? Why is it restricted by compiler ?

Core Java

Ans. Because Abstract class is incomplete i.e there are abstract methods that needs to be defined by extending classes.

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Q681. What was the need of creating an abstract class in Java when we cannot instantiate an object of it ?

Core Java

Ans. The objective of an abstract class is to provide an interface as well as code reuse. Though we cannot instantiate an instance of abstract class but we can reuse the code by extending such a class. Moreover abstract class provides interfacing to outside components just like interfaces.

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Q682. Is array an object in Java ? How can you prove that ?

Core Java

Ans. Yes.

There are 2 ways this can be confirmed

1. Accessing object class methods using array reference.

2. Checking if the array is an instance of Object class

if (arrayRef instanceof Object)

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Q683. Write a program for 0 and cross games?

Core Java

^{This question was recently asked at 'Compro Technologies'.This question is still unanswered. Can you please provide an answer.}

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Q684. Why do we need Garbage collection ?

Core Java

Ans. Garbage collection mechanism frees up the memory that is no longer needed. In languages like C / C++ the deallocation needs to be done explicitly by the programmer and hence any leniency may result in memory leak. Garbage collection in java ensures that all unused memory is reclaimed and hence there are no memory leaks.Moreover it relieves the programmer from the hassle of carefully releasing all memory.

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Q685. What is a gobbler class ?

Core Java

Ans. A gobbler class take care of reading from a stream and optionally write out to another stream. Allows for non blocking reads when invoking a process through Runtime.exec(). Moreover the user can specify a callback that is called whenever anything is read from the stream.

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Q686. Does Java allows inter thread communication ?

Core Java

Ans. Yes. Using wait and notify methods.

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Q687. Difference between int and short data types ?

Core Java

Ans. Both holds numeric values. short is a 16-bit signed two's complement integer whereas int is a 32-bit signed two's complement integer.

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Q688. Can a constructor have a private access specifier ?

Core Java

Ans. Yes, declaring a constructor private means disabling the creation of object that way using new operator.

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Q689. What does 'canonical representation' in Java mean ?

Core Java

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Q690. Can an object be assigned to multiple references ?

Core Java

Ans. Yes we can assign an object to multiple references like following

String str1 = new String("Hello World");
String str2 = str1;

Now both str1 and str2 points to "Hello World" in memory.

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