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!!! Java Frequently Asked Questions !!!

Q. When we go for Abstract and Interface in Java?

SCJP 1.5/1.6 Exam Kit

!!!Answer!!!- From Technical Expert

When the sub-types behaviour is totally different then you use an interface, when the sub-types behaviour is partially common and different with respect to the supertype an abstract class is used.
In an abstract class the partially common behaviour is given a concrete implementation.
Since there is no common behaviour between an interface and a sub-type an interface does not have an implementation for any of its behaviour.
For Example - Abstract Class
abstract public class Animal {
public eatChicken(){
System.out.println("Eat Chicken");
}

}

public Lion extends Animal{
}
public Tiger extends Animal{
}

Both Lion and Tiger class has common behaviour eatChicken() and all the implementaion put into eatChicken() method of super calss.
so we go for abstract class.

Example- Interface

Interface Animal{
public eat();
}
public Lion implements Animal{
public eat(){
System.out.println("Lion eat Non Veg");
}
}
public Cow implements Animal{
public eat(){
System.out.println("Cow eat Veg");
}
}
Both Lion and Cow class has different behaviour for eat() and they have different implementations. so we go for Interface.

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