Simple doubt... Please help

[dmjpro]

look at this example.....

[code=java]
class InterfaceTest1
{
void test();
}
class ClassTest1
{
public void test(){}
}
class ClassTest2 extends ClassTest1 implements Interface
{
public void test(){} //Method overriden or method implementation?
}
[/code]

How it is posiible ......???

Please explain.

Kind regards,
Dmjpro.

[r035198x]

look at this example.....

[code=java]
class InterfaceTest1
{
void test();
}
class ClassTest1
{
public void test(){}
}
class ClassTest2 extends ClassTest1 implements Interface
{
public void test(){} //Method overriden or method implementation?
}
[/code]

How it is posiible ......???

Please explain.

Kind regards,
Dmjpro.

You got your class names and variable names wrong there dj. The method test is overriden of course and also the class satisfies the contract of the interface by implementing the method test as well. Normally this is not done because it's useless. Either you're using an abstract class or an interface. And choice is usually obvious.

[dmjpro]

You got your class names and variable names wrong there dj. The method test is overriden of course and also the class satisfies the contract of the interface by implementing the method test as well. Normally this is not done because it's useless. Either you're using an abstract class or an interface. And choice is usually obvious.

Actually what happens to me.
Today I see the Collection interface carefully.
There I see a method int hashCode() and the class which by default extends Object and implements Collection interface or it's sub-interfaces have to implement the method int hashCode().
That's why I questioned it.

Kind regards,
Dmjpro.

[r035198x]

Actually what happens to me.
Today I see the Collection interface carefully.
There I see a method int hashCode() and the class which by default extends Object and implements Collection interface or it's sub-interfaces have to implement the method int hashCode().
That's why I questioned it.

Kind regards,
Dmjpro.

It is important for concrete classes to implement it that's why it was included in that interface.

[dmjpro]

It is important for concrete classes to implement it that's why it was included in that interface.

Yup right.
But Object class itself contains int hashCode() method.

Kind regards,
Dmjpro.

[JosAH]

Actually what happens to me.
Today I see the Collection interface carefully.
There I see a method int hashCode() and the class which by default extends Object and implements Collection interface or it's sub-interfaces have to implement the method int hashCode().
That's why I questioned it.

Kind regards,
Dmjpro.

You don't *have to* implement hashCode() and its compadre equals(), those
methods are just part of the interface to emphasize that you should reimplement
them in several occasions. Read the Collection API docs for those two methods.
And of course, if you don't implement them the interface contract is still fulfilled
because the Object class implements them both (but not the way some collections
expect them to be implemented).

kind regards,

Jos