thisdemo.java

这是《Java 2 简明教程(第2版)》一书配套的源代码。

class Point
{
  protected int x,y;
  Point(int a, int b)
  {
      setPoint(a,b);
  }
  public void setPoint(int a,int b)
  {
     x=a;
     y=b;
  }
}

class Line extends Point
{
     protected int x,y;
     Line(int a,int b)
     { 
        super(a,b);
        setLine(a,b);
    }
   
 
   public void setLine(int x,int y)
   {
     this.x=x+x;
     this.y=y+y;
   }
 
   public double length()
   {
     int x1=super.x,y1=super.y,x2=this.x,y2=this.y; 
     return Math.sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
   }

   public String toString()
   {
     return"直线端点：["+super.x+super.y+"]["+x+"."+y+"]直线长度："+this.length();
   }
}
 
public class ThisDemo
{
   public static void main(String args[])
    {
      Line line=new Line(20,20);
      System.out.println("\n"+line.toString());
    }
 }