将已存在类的对象放到新类中
package 第三章类的重用;
public class 类的组合 {
public static class Point{
private int x,y;
public Point(int x,int y){this.x=x;this.y=y;}
public int GetX(){return x;}
public int GetY(){return y;}
}
static class Line{
// 点类的构造方法,构造两个点对象
private Point p1,p2;
Line(Point a,Point b){
p1 = new Point(a.GetX(),a.GetY());
p2 = new Point(b.GetX(),b.GetY());
}
public double Length(){
return (Math.sqrt(Math.pow(p2.GetX()-p1.GetX(),2) + Math.pow(p2.GetY()-p1.GetY(),2)));
}
}
public static void main(String[] args) {
Point p1=new Point(1,2);
Point p2=new Point(3,4);
Line l1=new Line(p1,p2);
}
}
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