상속

class Point{
	private int x,y;
	public void set(int x, int y) {
		this.x=x;
		this.y=y;
	}
	public void showPoint() {
		System.out.println("(" + x + "," + y + ")");
	}
}

class ColorPoint extends Point{
	private String color;
	public void setColor(String color) {
		this.color=color;
	}
	public void showColorPoint() {
		System.out.print(color);
		showPoint();
	}
}

public class ColorPointEx {
	public static void main(String[] args) {
		Point p=new Point();
		p.set(1, 2);
		p.showPoint();
		
		ColorPoint cp=new ColorPoint();
		cp.set(3, 4);
		cp.setColor("red");
		cp.showColorPoint();
	}
}

supper()이용한 생성자 선택

class Point{
	private int x,y;
	public Point() {
		this.x=this.y=0;
	}
	public Point(int x, int y) {
		this.x=x;
		this.y=y;
	}
	public void showPoint() {
		System.out.println("(" + x + "," + y + ")");
	}
}

class ColorPoint extends Point{
	private String color;
	public ColorPoint(int x, int y, String color) {
		super(x,y);
		this.color=color;
	}
	public void showColorPoint() {
		System.out.println(color);
		showPoint();
	}
}

public class SuperEx {
	public static void main(String[] args) {
		ColorPoint cp=new ColorPoint(5,6,"blue");
		cp.showColorPoint();
	}
}