先说java中实现多线程常用的两种方式：
   1：继承Thread类，并重写run()方法
   2：实现Runnable接口，实现run方法
实际上Thread类也是实现了Runnable接口

[Java] 纯文本查看 复制代码

public class Thread implements Runnable {
  ........
｝

而Runnable接口只定义了一个run方法

[AppleScript] 纯文本查看 复制代码

@FunctionalInterface
public interface Runnable {
    /**
     * When an object implementing interface <code>Runnable</code> is used
     * to create a thread, starting the thread causes the object's
     * <code>run</code> method to be called in that separately executing
     * thread.
     * <p>
     * The general contract of the method <code>run</code> is that it may
     * take any action whatsoever.
     *
     * @see     java.lang.Thread#run()
     */
    public abstract void run();
}

我们需要实现的多线程业务逻辑，都需要在run方法内实现。

而start()是Thread中定义的方法，以下是start()方法的源码

[Java] 纯文本查看 复制代码

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();
            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 */
            }
        }
    }

start()通过调用本地native方法start0来启动一个线程，本地方法内最终会调用run方法，这样就可以实现在另一个线程中运行我们需要的代码。
而单独运行run()方法，就跟我们调用普通接口实现方法一样了，并不会启动新的线程.
总结：
1、start()方法运行时，本地启动新的线程，线程中会调用run方法，程序不需要等待run方法执行完毕再执行后面的程序;

2、run()方法是我们编写需要新的线程执行代码的方法，单独运行是不会有多线程效果的。

先说java中实现多线程常用的两种方式：
   1：继承Thread类，并重写run()方法
   2：实现Runnable接口，实现run方法
实际上Thread类也是实现了Runnable接口

[Java] 纯文本查看 复制代码

public class Thread implements Runnable {
  ........
｝

而Runnable接口只定义了一个run方法

[AppleScript] 纯文本查看 复制代码

@FunctionalInterface
public interface Runnable {
    /**
     * When an object implementing interface <code>Runnable</code> is used
     * to create a thread, starting the thread causes the object's
     * <code>run</code> method to be called in that separately executing
     * thread.
     * <p>
     * The general contract of the method <code>run</code> is that it may
     * take any action whatsoever.
     *
     * @see     java.lang.Thread#run()
     */
    public abstract void run();
}

我们需要实现的多线程业务逻辑，都需要在run方法内实现。

而start()是Thread中定义的方法，以下是start()方法的源码

[Java] 纯文本查看 复制代码

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();
            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 */
            }
        }
    }

start()通过调用本地native方法start0来启动一个线程，本地方法内最终会调用run方法，这样就可以实现在另一个线程中运行我们需要的代码。
而单独运行run()方法，就跟我们调用普通接口实现方法一样了，并不会启动新的线程.
总结：
1、start()方法运行时，本地启动新的线程，线程中会调用run方法，程序不需要等待run方法执行完毕再执行后面的程序;

2、run()方法是我们编写需要新的线程执行代码的方法，单独运行是不会有多线程效果的。