Runnable：

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

Runnable是个只有一个方法的接口。 

Thread：

publicclass Thread implements Runnable {    /* What will be run. */    private Runnable target;    /**     * 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.     * 
     * Subclasses of Thread should override this method.     *     * @see     #start()     * @see     #stop()     * @see     #Thread(ThreadGroup, Runnable, String)     */    @Override    public void run() {        if (target != null) {            target.run();        }    }}

Thread实现了Runnable接口，而且还组合了一个Runnable，可以看出，实现的方法内部是调用组合类的方法，这其实就是装饰模式。