JAVA | 23

每当用 java 命令解释一个程序类时，操作系统就会启动一个进程，而 main 只是这新进程上的一个子线程。

JVM 启动的时候会执行 main 线程和 gc 线程。

线程的命名与取得：取得的是执行当前本方法的线程名。

class MyThread implements Runnable{    @Override    public void run() {        System.out.println(Thread.currentThread().getName());    }}public class Main {    public static void main(String[] args) {        MyThread myThread1 = new MyThread();        MyThread myThread2 = new MyThread();        new Thread(myThread1).start();        new Thread(myThread2,"Thread A").start();        myThread1.run();    }}

默认情况下，在休眠的时候如果设置了多个线程对象，那么所有的线程对象将一起进入 run 方法（先后顺序实在是太短了）。

class MyThread implements Runnable{    @Override    public void run() {        for(int i = 0; i < 10; i ++) {            try {                Thread.sleep(1000);            } catch (InterruptedException e) {                e.printStackTrace();            }            System.out.println(Thread.currentThread().getName());        }    }}public class Main {    public static void main(String[] args) {        MyThread myThread1 = new MyThread();        new Thread(myThread1,"Thread A").start();        new Thread(myThread1,"Thread B").start();        new Thread(myThread1,"Thread C").start();        new Thread(myThread1,"Thread D").start();    }}

优先级越高的线程对象越有可能先执行

主线程的优先级别是中等。

class MyThread implements Runnable{    @Override    public void run() {        for(int i = 0; i < 10; i ++) {            try {                Thread.sleep(1000);            } catch (InterruptedException e) {                e.printStackTrace();            }            System.out.println(Thread.currentThread().getName() + " " + i);        }    }}public class Main {    public static void main(String[] args) {        MyThread myThread1 = new MyThread();        Thread A = new Thread(myThread1,"Thread A");        Thread B = new Thread(myThread1,"Thread B");        Thread C = new Thread(myThread1,"Thread C");        Thread D = new Thread(myThread1,"Thread D");        A.setPriority(Thread.MAX_PRIORITY); //10        B.setPriority(Thread.MIN_PRIORITY); //1        C.setPriority(Thread.NORM_PRIORITY); //5        D.setPriority(Thread.MIN_PRIORITY); //1        A.start();        B.start();        C.start();        D.start();        System.out.println(Thread.currentThread().getName() + " " + Thread.currentThread().getPriority());    }}