java的一个小问题,高手过来指点......

//Calling constructors with "this"               用“this”调用构造函数

public class Flower
{
    int petalCount = 0;
    String s = "initial value";
    Flower(int prtals)
    {
        petalCount = prtals;
        System.out.println("Constructor w/ String arg only, prtalcount = " + petalCount);
    }
   
    Flower(String ss)
    {
        System.out.println("Constructor w/ String arg only, s = " + ss);
        s = ss;
    }
   
    Flower(String s, int petals)
    {
        this(petals);                    //这个语句什么意思?是怎么执行的?
        //!  this(s);  //Can't call two!      //不能叫两个！
        this.s = s;  //Another use of "this"         // “this”的另一个用法
        System.out.println("String & int args");          //字符串和字符串
    }
   
    Flower()
    {
        this("hi", 47);
        System.out.println("default constructor (no args)");               //缺省构造函数（无ARG）
    }
   
    void printPetalCount()
    {
        //! this(11);     //Not inside non - constructor!           不在非构造函数之内！
        System.out.println("petalCount = " + petalCount + " s = " + s);
    }
   
    public static void main(String[] args)
    {
        Flower x = new Flower();
        x.printPetalCount();
    }
}