Abstract class for Java

Rules for abstract classes:

1. Abstract classes can have no abstract methods, classes with abstract methods must be abstract classes

2. Non-abstract classes inherit abstract classes, and all abstract methods of the abstract class must be implemented

3. Abstract classes, like ordinary classes, can have method implementations and properties

4. Abstract classes cannot be instantiated

5. Abstract classes cannot be declared final.

The existence of an abstract class is for the quilt class to inherit, and the final decorated class indicates that the class cannot be inherited, so using final to modify the abstract class is a few meanings?

Abstract class example{    publicabstractvoid foo ();   declare only, do not implement }classextends  example{    public Abstract void foo () {        System.out.println ("test for Abstract of class!" );    }}

Abstract class for Java