Thread中的run()和start()的区别

啥都不用说，先上一个例子：

/** * @author I321023 * different between function run and function start in class Thread */public class TestRS extends Thread{    public TestRS(String name) {        super(name);    }    @Override    public void run() {        System.out.println("Thread is running~");    }    public static void main(String[] args) {        TestRS tRs = new TestRS("My thread");        tRs.run();//Thread is running~        tRs.start();//Thread is running~    }}

对于上面这个简单的程序的输出结果大家应该都没有疑问，但是应该发现run(),start()最终的结果都是调用了run()方法，那他两是不是一样的呢？再来看一段代码：

/** * @author I321023 *  * different between function run and function start in class Thread */public class TestRS extends Thread{    public TestRS(String name) {        super(name);    }    @Override    public void run() {        System.out.println(Thread.currentThread().getName() + " is running!");    }    public static void main(String[] args) {        TestRS tRs = new TestRS("My thread");        tRs.run();//main is running!        tRs.start();//My thread is running!    }}

这里大家可以清楚的看到这两个的区别，下面总结一下：
1. tRs.run();//main is running!是在主线程main中调用的，并没有新线程
2. tRs.start();//My thread is running!start()方法会新启动一个线程，启动后，这个新线程会调用run()方法，这才是我们想要的多线程

下面我们来看一下这两个方法的源码：

/**     * If this thread was constructed using a separate     * <code>Runnable</code> run object, then that     * <code>Runnable</code> object's <code>run</code> method is called;     * otherwise, this method does nothing and returns.     * <p>     * Subclasses of <code>Thread</code> should override this method.     *     * @see     #start()     * @see     #stop()     * @see     #Thread(ThreadGroup, Runnable, String)     */    @Override    public void run() {        if (target != null) {//target是Runnable对象，如果不为空直接调用Runnable的成员方法run()，并不会新建线程            target.run();        }    }

/**     * Causes this thread to begin execution; the Java Virtual Machine     * calls the <code>run</code> method of this thread.     * <p>     * The result is that two threads are running concurrently: the     * current thread (which returns from the call to the     * <code>start</code> method) and the other thread (which executes its     * <code>run</code> method).     * <p>     * It is never legal to start a thread more than once.     * In particular, a thread may not be restarted once it has completed     * execution.     *     * @exception  IllegalThreadStateException  if the thread was already     *               started.     * @see        #run()     * @see        #stop()     */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();        /* 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();//调用本地方法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 */            }        }    }    private native void start0();//会新开一个线程，新线程再调用run()方法

PS:从上面两段源码，大家应该可以很清楚看到run()和start()的区别，当多线程的时候千万不要弄错了。。。