java abstract classes and abstract methods

Add abstract declaration
only statement did not realize, class contains abstract methods must be abstract class, abstract class can be defined inside a common method
subclasses of an abstract class, you must override abstract methods inside the
abstract class can not be instantiated by new own object, but the object can be instantiated by a new subclass can be used to abstract class is inherited

public abstract class test<E> {

abstract public void f();

}

class b extends test{

public void f()
{
    System.out.println("yes");
}

}