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Q:

I don't want my class to be inherited by any other class. What should i do?

Answer

You should declared your class as final. But you can't define your class as final, if it is an abstract class. A class declared as final can't be extended by any other class.

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Subject: Java

Q:

What is the impact of declaring a method as final?

Answer

A method declared as final can't be overridden. A sub-class can't have the same method signature with a different implementation.

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Subject: Java

Q:

What is the difference between creating a thread by extending Thread class and by implementing Runnable interface? Which one should prefer?

Answer

When creating a thread by extending the Thread class, it is not mandatory to override the run method (If we are not overriding the run method , it is useless), because Thread class have already given a default implementation for run method. But if we are implementing Runnable , it is mandatory to override the run method. The preferred way to create a thread is by implementing Runnable interface, because it give loose coupling.

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Subject: Java

Q:

What are the the different ways for creating a thread?

Answer

A thread can be created by subclassing Thread, or by implementing the Runnable interface.

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Subject: Java

Q:

What are the restrictions when overriding a method ?

Answer

Overridden methods must have the same name, argument list, and return type (i.e., they must have the exact signature of the method we are going to override, including return type.)


The overriding method cannot be less visible than the method it overrides( i.e., a public method cannot be override to private).


The overriding method may not throw any exceptions that may not be thrown by the overridden method

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Subject: Java

Q:

What is inheritance?

Answer

Inheritance is the ability to create new classes based on existing classes. It is useful to reuse existing code.

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Subject: Java
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Q:

What is the security mechanism used in java?

Answer

Java uses sand box security model.

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Subject: Java

Q:

What is the difference between array and ArrayList ?

Answer

Array is collection of same data type. Array size is fixed, It cannot be expanded.


 


But ArrayList is a growable collection of objects.ArrayList is a part of Collections Framework and can work with only objects.

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Subject: Java