抽象类

class Pencil
{
    String name;
    Pencil(){}
    Pencil(String name)
    {
        this.name = name;
    }
    public void write()
    {
        System.out.println("write quickly...");
    }
}

interface Eraser
{
    public static final String color = "白色";
    public abstract void clean();
}
//()
class PencilWithEraser extends Pencil implements Eraser
{
    PencilWithEraser(){}
    PencilWithEraser(String name)
    {
        super(name);
    }
    //public
    public void write()
    {
        System.out.println("super "+ super.name+ "PencilWithEraser‘s name...");
        System.out.println("this "+ this.name+ "PencilWithEraser‘s name...");
    }
    //void clean()
    public void clean()
    {
        System.out.println("ERROR, use Eraser...");
    }
}

public class jiekou 
{
    public static void main(String[] args) 
    {
        PencilWithEraser p = new PencilWithEraser("中华");
        p.write();
        p.clean();
        System.out.println(p.color);
        System.out.println(PencilWithEraser.color);
    }
}