Could not an abstract class be extended (inherited from) in Java?

Question

Should a class have an abstract keyword before it? Or do you need to have unrealized (abstract) methods? Can any normal class propagate?

Answer 1

Can any normal class propagate?

Yes :) If it does not have a final modifier.

Answer 2

Yes, all methods that are not final (static are also slightly different from the rest) can be overridden if the class itself is not declared final. Abstract methods are used only if you do not provide any implementation in the base class.

Answer 3

, abstract, abstract , , , .

AbstractClass abs = new ChildClass();

Answer 4

, . , . ,

DifferentString extends String

public String toString()
{
    return "Something different";
}

, .

:

http://docs.oracle.com/javase/tutorial/java/IandI/abstract.html

Answer 5

, , , , , , .

Answer 6

, , .

class Foo {
    //some code here
}

class Boo extends Foo {

}

Answer 7

. , .

You can extend any class until it is final.

Edit: what I wanted to say is that it is preferable to host Unimplemented methods in interfaces. Sorry for the poor wording. There may be unrealized methods in abstract classes, although in the end you will have a complex and rigid hierarchy. ,