Abstract method

[Ah Ming]

Hi,

I am a beginner of Java programmer. There is a question about the
following program segment. Why class ABC must be defined as Abstract
when aMethod has int b?

interface DEF {
public void aMethod(int a);
}

Abstract class ABC implements DEF {
public void aMethod(int a, int b) {
}
}

Thanks!

 

[Tjerk Wolterink]

Hi,

I am a beginner of Java programmer. There is a question about the
following program segment. Why class ABC must be defined as Abstract
when aMethod has int b?

interface DEF {
public void aMethod(int a);
}

Abstract class ABC implements DEF {
public void aMethod(int a, int b) {
}
}

Thanks!

aMethod in class ABC is a different method than aMethod from DEF, because of the
differen arguments lengths.

So ABC.aMethod(int, int) does not override aMethod(int) from DEF.
But because ABC implements DEF it should implement the methods from interface DEF.
IT does not do that and the only way to allow that is to make ABC abstract.
When you extend ABC you should implement the DEF internface, so then you should
define aMethod(int)

 

[George W. Cherry]

Hi,

I am a beginner of Java programmer. There is a question about the
following program segment. Why class ABC must be defined as Abstract
when aMethod has int b?

interface DEF {
public void aMethod(int a);
}

Abstract class ABC implements DEF {
public void aMethod(int a, int b) {
}
}

A class (e.g., ABC) which purports to implement an
interface (e.g., DEF) must implement all the interface's
methods--or it must declare itself abstract. DEF does
not implement

public void aMethod(int a);

ABC implements a different method

public void aMethod(int a, int b)

George