java - 为什么我的代码中第一个 Thread.activeCount() 返回 1 而另一个返回 2？

Question

这是我的申请:

public class NamedThread extends Thread {
    /* This will store name of the thread */

    String name;

    @Override
    public void run() {
//Will store the number of threads
        int count = 0;
        while (count <= 3) {
//Display the number of threads
            System.out.println(Thread.activeCount());
//Display the name of the currently running thread
            name = Thread.currentThread().getName();
            count++;
            System.out.println(name);
            if (name.equals("Thread1")) {
                System.out.println("Marimba");
            } else {
                System.out.println("Jini");
            }
        }
    }

    public static void main(String args[]) {
        NamedThread objNamedThread = new NamedThread();
        objNamedThread.setName("Thread1");
//Display the status of the thread, whether alive or not
        System.out.println(Thread.currentThread().isAlive());
        System.out.println(objNamedThread.isAlive());
        /*invokes the start method which in turn will call
         * run and begin thread execution
         */
        objNamedThread.start();
        System.out.println(Thread.currentThread().isAlive());
        System.out.println(objNamedThread.isAlive());
    }
}

输出是:

true
false
true
true
1
Thread1
Marimba
2
Thread1
Marimba
2
Thread1
Marimba
2
Thread1
Marimba

我的申请有什么问题，为什么？谢谢!

Answer 1

public static void main(String[] args) {
    System.out.println(Thread.activeCount());

    //doSomething()
}

上面的代码输出2

GC占用一个线程，所以你得到2个，而不是1

该函数是为调试而设计的

如果你在 Debug模式下运行，你会得到 1