使用Super调用父类的构造方法

/*一个类的构造函数的功能是给其成员变量赋值*/
package learnJava;

class S{
	int x,y;
	S(){
		x=100;
		y=200;
	}
	S(int x,int y){
		this.x=x;
		this.y=y;
	}
}
class R extends S{
	int z;
	R(int x,int y){
		super(x,y);
		z=300;
	}
	R(){
		z=300;
	}
	public void f(){
		System.out.printf("x=%d,y=%d,z=%d\n", x,y,z);
	}
}

public class Example6 {
	public static void main(String args[]){
		R r1=new R(10,20);
		r1.f();
		R r2=new R();
		r2.f();
	}
}