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浅析Thread类run()和start()的区别
1.先看看jdk文档
1 void run() 2 If this thread was constructed using a separate Runnable run object, then that Runnable object‘s run method is called; otherwise, this method does nothing and returns.
1 void start() 2 Causes this thread to begin execution; the Java Virtual Machine calls the run method of this thread.
线程调用run()方法是直接执行其run方法(正常情况)。
线程调用start()方法后进入准备状态,等待CPU的调度,当切换到该线程时,线程进入运行状态,执行run()方法。
既然都是执行线程的run方法,为什么不直接调用run方法?
2.再看代码
1 public class Main { 2 3 public static void main(String[] args) { 4 Mythread t = new Mythread(); 5 Thread thread1 = new Thread(t); 6 Thread thread2 = new Thread(t); 7 System.out.println("begin = " + System.currentTimeMillis()); 8 thread1.setName("我是线程1"); 9 thread2.setName("我是线程2"); 10 thread1.run(); 11 thread2.start(); 12 System.out.println("end = " + System.currentTimeMillis()); 13 } 14 } 15 16 class Mythread extends Thread{ 17 public void run() { 18 try { 19 System.out.println("threadName: "+this.currentThread().getName()+" begin"); 20 Thread.sleep(1000); 21 System.out.println("threadName: "+this.currentThread().getName()+" end"); 22 } catch (InterruptedException e) { 23 e.printStackTrace(); 24 } 25 } 26 }
运行结果:
可以发现直接调用run方法时是被主线程当做普通的方法调用,并不是真正的多线程。
浅析Thread类run()和start()的区别
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