Java Questions

Q:

What is the purpose of declaring a variable as final?

Answer A final variable's value can't be changed. final variables should be initialized before using them.
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Q:

Why interface method is always public?

Answer

To make this method available to every implementation class

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Subject: Java
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Q:

What is Overloading Polymorphism?

Answer

Overloading allows multiple functions to exist with same name but different parameters. Again if you take bike as an example, it has a function “Start” with two forms i.e. ’Auto Start’ and ’kick start’.

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Q:

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

Answer

A protected method may only be accessed by classes or interfaces of the same package or by subclasses of the class in which it is declared.

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Q:

What are the basic interfaces of Java Collections Framework ?

Answer

Java Collections Framework provides a well designed set of interfaces and classes that support operations on a collections of objects. The most basic interfaces that reside in the Java Collections Framework are:


Collection, which represents a group of objects known as its elements.


Set, which is a collection that cannot contain duplicate elements.


List, which is an ordered collection and can contain duplicate elements.


Map, which is an object that maps keys to values and cannot contain duplicate keys.

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Q:

What is MultiThreading?

Answer

Executing two or more blocks (threads) of a program at a time is called MultiThreading.

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Q:

What is final method?

Answer

Final method is a method defined in the super class with final modifier.


We cannot overriding final method of super class in the sub class.


EX:


 Class Sample {


   final void funOne() {


   }


   void funTwo() {


   }


}


Class Sub extends Sample {


  void funOne() { // overriding is not allowed


  }


  viod funTwo() { //overriding is allowed


  }


}

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Q:

Can you access non static variable in static context ?

Answer

A static variable in Java belongs to its class and its value remains the same for all its instances. A static variable is initialized when the class is loaded by the JVM. If your code tries to access a non-static variable, without any instance, the compiler will complain, because those variables are not created yet and they are not associated with any instance.

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