java继承实例。

定义了一个点类point，然后线条类line继承了point类，正方形类Suare继承point类。

package test;

import javax.swing.*;
public class test {
    public static void main(String args[]){
        line AB = new line();
        System.out.println("AB的第一个坐标为:x="+AB.EGetx()+",y="+AB.EGety()+"."+"AB的第二个坐标为:x="+AB.EGetx()+",y="+AB.FGety()+".");
        Square ABCD = new Square();
        System.out.println("ABCD的第一个坐标为:"+ABCD.Get1x()+","+ABCD.Get1y()+"."
                            +"ABCD的第二个坐标为:x="+ABCD.Get2x()+","+ABCD.Get2y()+"."
                            +"ABCD的第三个坐标为:x="+ABCD.Get3x()+","+ABCD.Get3y()+"."
                            +"ABCD的第四个坐标为:x="+ABCD.Get4x()+","+ABCD.Get4y()+".");
    }
}
class point{
    private int x,y;
    static int pCount = 0;
    point(){x=10;y=20;pCount++;System.out.println("创建一个point，这个point为第："+pCount+"个.");}
    point(int x,int y){this.x=x;this.y=y;pCount++;System.out.println("创建一个point，这个point为第："+pCount+"个.");}
    static int GeipCount(){return pCount;}
    int Getx(){return x;}
    int Gety(){return y;}
}
class line extends point{
    static int lCount = 0;
    private    point E;
    private    point F;
    private float range;
    line()
    {
        E = new point();
        F = new point(1,2);
        range=1.5f;
        lCount++;
        System.out.println("创建一个line，这个line为第："+lCount+"个.");
    }
    line(point E,point F,float range)
    {
        this.E=E;
        this.F=F;
        this.range=range;
        lCount++;
        System.out.println("创建一个line，这个line为第："+lCount+"个.");
    }
    static int GeilCount(){return lCount;}
    int EGetx(){return E.Getx();}
    int EGety(){return E.Gety();}
    int FGetx(){return F.Getx();}
    int FGety(){return F.Gety();}
}
class Square extends point{
    private point A;
    private int range;
    static int sCount = 0;
    Square(){A = new point();range = 1;sCount++;System.out.println("创建一个Square，这个line为第："+sCount+"个.");}
    Square(point A){this.A = A;range = 1;sCount++;System.out.println("创建一个Square，这个line为第："+sCount+"个.");}
    Square(point A,int range){this.A = A;this.range = range;sCount++;System.out.println("创建一个Square，这个line为第："+sCount+"个.");}
    int Get1x(){return A.Getx();}
    int Get1y(){return A.Gety();}
    int Get2x(){return A.Getx()+range;}
    int Get2y(){return A.Gety();}
    int Get3x(){return A.Getx();}
    int Get3y(){return A.Gety()+range;}
    int Get4x(){return A.Getx()+range;}
    int Get4y(){return A.Gety()+range;}
}