class Point       //平面上點的類
{   private double x,y;

    public Point(double a,double b)
    {   x=a;
        y=b;
    }

    public double x( )
    {   return x;
    }

    public double y( )
    {   return y;
    }

    public boolean equals(Point p)
    {   return (x==p.x && y==p.y);
    }

    public String toString( )    // java 中的特殊方法
    {   return new String("("+x+","+y+")");
    }
}

public class PointDemo
{   public static void main(String args[ ])
    {   Point p=new Point(2,3);
        System.out.println("p:"+p);    // p 等價于 p.toString( )
        Point q=new Point(7,4);
        System.out.println("q:"+q);
        if(q.equals(p)) System.out.print("q equals p");
        else System.out.println("q does not equal p");
        System.out.println( );
        q=new Point(2,3);
        System.out.println("p:"+p);
        System.out.println("q:"+q);
        if (q.equals(p)) System.out.println("q equals p");
        else System.out.println("q does not equal p");
    }
}