March 29th, 2015, Thread Name is odd by increasing 1

public class Fabric extends Thread{
    
    public static void main(String args[]){
        Thread t = new Thread(new Fabric());
        Thread t2 = new Thread(new Fabric());
        Thread t3 = new Thread(new Fabric());
        
        t.start();
        t2.start();
        t3.start();
    }

    public void run(){
        System.out.println(Thread.currentThread().getName() + ": " + i);
    }
}

这段代码的输出为 1，3，5 （无序）

但如果指定线程名则为1，2，3：

public class Fabric extends Thread{
    
    public static void main(String args[]){
        Thread t = new Thread(null, new Fabric(), "1");
        Thread t2 = new Thread(null, new Fabric(), "2");
        Thread t3 = new Thread(null, new Fabric(), "3");
        
        t.start();
        t2.start();
        t3.start();
    }

    public void run(){
        System.out.println(Thread.currentThread().getName() + ": " + i);
    }
}