其实有时候不能简单说哪种设计用到了哪些设计模式，设计模式本身就是对很多代码设计经验的总结。

模板模式

模板模式的应用就比较好理解了。在创建线程一般使用构建 Thread 类或者实现 Runnable 接口（这种说法是错误的，最起码是不严谨的，在 JDK 中代表线程的就只有 Thread 这个类，线程的执行单元就是 run() 方法，你可以通过继承 Thread 然后重写 run() 方法实现自己的业务逻辑，也可以实现 Runnable 接口实现自己的业务逻辑），启动线程是使用的 start() 方法，但是具体业务逻辑还是在 run() 方法中。

/**
     * 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();
            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 */
            }
        }
    }

 这样可以将业务逻辑和线程的逻辑分离。在​​模板设计模式在Thread的应用​​中看到了一个挺好的例子：

/**
 * Description
 * <p>
 * </p>
 * DATE 2018/10/26.
 *
 * @author caichengzhang.
 */
public class Template {
 
    public Template() {
    }
 
    public final void start(){
        System.out.println("stat方法启动！");
        run();
        System.out.println("start方法结束！");
    }
 
    public void run(){}
 
    public static void main(String[] args) {
 
        Template template = new Template(){
            @Override
            public void run() {
                System.out.println("run方法开始运行！");
            }
        };
 
        template.start();
    }
 
}

策略模式

结合上面的 Thread 的 start() 方法，注释说明 start() 方法执行的是它的 run() 方法，再看看 Thread 的 run() 方法，如果构造传入 Runnable，就执行 Runnable 的 run() 方法，否则就需要重写 Thread 的 run() 方法。

/**
     * 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.run();
        }
    }
/* What will be run. */
    private Runnable target;

无论是 Runnable 的 run() 方法，还是 Thread 类本身的 run() 方法（事实上 Thread 类也是实现了 Runnable 接口）都是想将线程的控制本身和业务逻辑的运行分离开来，达到职责分明、功能单一的原则，这一点与 GoF 设计模式中的策略设计模式很相似。

这个 Runnable 就是策略接口，针对不同的策略实现，执行相应的方法。这样对策略进行不同的实现即可。

package com.example.threaddesign;

/**
 * @author Dongguabai
 * @date 2018/12/2 20:58
 */
public class ThreadTest {

    public static void main(String[] args) {
        Thread thread = new Thread(new Strategy1(), "执行者");
        thread.start();
    }

    static class Strategy1 implements Runnable {

        @Override
        public void run() {
            System.out.println("策略一");
        }
    }

    static class Strategy3 implements Runnable {

        @Override
        public void run() {
            System.out.println("策略三");
        }
    }

    static class Strategy2 implements Runnable {

        @Override
        public void run() {
            System.out.println("策略二");
        }
    }
}