point.java

用java实现继承实例

public class Point {
	protected double x;
	protected double y;
	protected double distance;
	Point (){
		setX(0);
		setY(0);
	}
	Point (double x,double y){
		setX(x);
		setY(y);
	}
	public void setX (double x){
		this.x=x;
		updateDistance();
	}
	public void setY (double y){
		this.y=y;
		updateDistance();
	}
	public double x (){
		return x;
	}
	public double y(){
		return y;
	}
	public double distanceFromOrigin (){
		return distance;
	}
	public String toString (){
		return "<"+ x + "," + y + ">";
	}
	protected void updateDistance (){
		distance = Math.sqrt(x*x + y*y);
	}
}