线程方法调用没有Thread实例

Question

为什么这个类在第11行编译没有错误，以及如何解释输出的最后一行：

class Bang extends Thread {

    static Thread t1;

    public static void main(String[] args) throws Exception {
        System.out.println("main thread ID = " + Thread.currentThread().getId());
        t1 = new Thread(new Bang());
        t1.setPriority(7);
        t1.setName("T1");
        t1.start();
    }

    public void run() {
        Thread th = Thread.currentThread();
        System.out.println(th.getId() + " " + th.getName() + "        "
                + th.getPriority() + "  " + th.toString() + "\n");
        System.out.println(getId() + " " + getName() + "  " + getPriority()
                + "  " + toString());
    }
}

输出：

主线程ID = 1 9 T1 7螺纹[T1,7，主要]

8 Thread-0 5 Thread [Thread-0,5，main]

谢谢，

Answer 1

@Tunaki是现货。我只是添加他说的话。

完全有三个Thread对象。

1. 主线程对象，它是一个java.lang.Thread
2. T1线程对象，它是一个java.lang.Thread
3. Bang Bang对象，这是一个Bang

请注意，主线程和T1线程 生成 作为单独的线程，而Bang线程 未生成 < /强>

您在run方法中打印的内容正在线程T1上运行。

Thread.currentThread().getId()将返回正在运行的主题 T1 的ID 9 。

this.getId()将返回 Bang 对象的ID 8 。还记得，你在T1对象之前创建了Bang对象吗？这就是为什么Bang拥有较小的id 8 ，而T1的较高的threadId 9 。

希望这会有所帮助。我已更新您的代码以打印有关哈希码和类详细信息的更多信息。输出应该给出清晰的图像。

代码：

class Bang extends Thread {

    static Thread t1;

    public static void main(String[] args) throws Exception {
        System.out.println("main thread ID = " + Thread.currentThread().getId());
        Bang bang = new Bang(); //Creating a local variable so we can print the object details.
        t1 = new Thread(bang);
        t1.setPriority(7);
        t1.setName("T1");
        threadInfo(bang);
        threadInfo(t1);
        t1.start();
    }
    public void run() {
        threadInfo(this);
    }
    public static void threadInfo(Thread argThreadObject) {
        System.out.println("===================================");
        Thread currentThreadObject = Thread.currentThread();
        printThreadInfo("currentThreadObject", currentThreadObject);
        printThreadInfo("argThreadObject", argThreadObject);
        System.out.println("===================================");
    }
    public static void printThreadInfo(String threadObjId, Thread threadObject) {
        System.out.println(
                threadObjId + ": " 
                + threadObject.getId() + ":"
                + threadObject.getName() + ":" 
                + threadObject.getPriority() + ":" 
                + threadObject.toString() + " instanceId: "
                + threadObject.hashCode() + "@"
                + threadObject.getClass().getName());
    }
}

输出

main thread ID = 1
===================================
currentThreadObject: 1:main:5:Thread[main,5,main] instanceId: 1113847530@java.lang.Thread
argThreadObject: 9:T1:7:Thread[T1,7,main] instanceId: 820485811@java.lang.Thread
===================================
===================================
currentThreadObject: 1:main:5:Thread[main,5,main] instanceId: 1113847530@java.lang.Thread
argThreadObject: 8:Thread-0:5:Thread[Thread-0,5,main] instanceId: 912528090@Bang
===================================
===================================
currentThreadObject: 9:T1:7:Thread[T1,7,main] instanceId: 820485811@java.lang.Thread
argThreadObject: 8:Thread-0:5:Thread[Thread-0,5,main] instanceId: 912528090@Bang
===================================