Java inheritance: How to achieve something similar to “multiple inheritance” when it is not allowed in Java?

Question

This is a question mostly about Java inheritance. I am developing a program which has 2 windows, both of which will be developed in separate classes which will extend JPanel

Answer 1

Prefer Composition over Inheritance

Include a FileThing in your JPanel subclass, instead of making it a FileThing and a JPanel.

Answer 2

You can do as below

public class Files extends JPanel{
}

public class FileSub1 extends Files{
}

public class FileSub2 extends Files{
}

Answer 3

I don't see why you need multiple inheritance. As far as I can tell you should be fine with a an abstract base class that implements the common methods:

public abstract class AbstractFilePanel extends JPanel
{
    public void commonMethod1() {}
}

public class FileSub1 extends AbstractFilePanel 
{
    public void sub1Method() {}
}

public class FileSub2 extends AbstractFilePanel 
{
    public void sub2Method() {}
}