Java多线程start（）方法原理解析

/** * @data 2019/11/8 - 下午10:29 * 描述：run()和start() */public class StartAndRunMethod {  public static void main(String[] args) {    Runnable runnable = new Runnable() {      @Override      public void run() {        System.out.println(Thread.currentThread().getName());      }    };    runnable.run();    new Thread(runnable).start();  }}

public synchronized void start() {    /**     * This method is not invoked for the main method thread or "system"     * group threads created/set up by the VM. Any new functionality added     * to this method in the future may have to also be added to the VM.     *     * A zero status value corresponds to state "NEW".     */    if (threadStatus != 0)      throw new IllegalThreadStateException();

  /*   * Java thread status for tools, default indicates thread 'not yet started'   */  private volatile int threadStatus;

 /* Notify the group that this thread is about to be started     * so that it can be added to the group's list of threads     * and the group's unstarted count can be decremented. */    group.add(this);

boolean started = false;    try {      start0();      started = true;    } finally {      try {        if (!started) {          group.threadStartFailed(this);        }      } catch (Throwable ignore) {        /* do nothing. If start0 threw a Throwable then         it will be passed up the call stack */      }    }  }

/** * @data 2019/11/8 - 下午11:57 * 描述：start不可以使用多次 */public class CantStartTwice {  public static void main(String[] args) {    Thread thread = new Thread();    thread.start();    thread.start();  }}