public class Rectangle {
// 受保護的member 
protected int x, y;
protected int width, height;
public Rectangle() {
x = y = 0;
width = height = 0;
}
public Rectangle(int x, int y, int width, int height) {
this.x = x;  this.y = y;
this.width = width;   this.height = height;
}
public int getX() { return x; }
public int getY() { return y; }
public int getWidth() { return width; }
public int getHeight() { return height; }
public int getArea() { return width*height; }
}

public class Cubic extends Rectangle {
protected int z;
protected int length;
public Cubic() {
z = 0;  length = 0;
}
public Cubic(int x, int y, int z,
int length, int width, int height) {
super(x, y, width, height);
this.z = z;
this.length = length;
}
public int getLength() { return length; }
public int getVolumn() { return length*width*height; }
}

public class UseProtected {
public static void main(String[] args) {
Cubic c1 = new Cubic(0, 0, 0, 10, 20, 30);
System.out.println("c1 volumn: " + c1.getVolumn());
}
}