命令模式在开源代码中的应用

迈不过友情╰ 2022-11-26 09:59 222阅读 0赞

命令模式的作用：将一个请求封装为一个对象，使发出请求的责任和执行请求的责任分割开。

### **案例** ###

JDK 中的线程 java.lang.Thread，使用了命令模式。

Thread 类的构造方法可以接收实现 Runnable 接口的对象，Runnable 的 run 方法可以理解为抽象命令，具体命令给程序员去实现。任务的接收与执行者是计算机的 CPU，任务的发起者是程序员。

public class Thread implements Runnable {
    	
    	private Runnable target;
    	
    	public Thread(Runnable target) {
            init(null, target, "Thread-" + nextThreadNum(), 0);
        }
    	
    	// 可以被重写，执行任务
    	public void run() {
            if (target != null) {
                target.run();
            }
        }
    	
    	// 线程启动，提交任务给 CPU
    	public synchronized void start() {
           
            if (threadStatus != 0)
                throw new IllegalThreadStateException();
    
            group.add(this);
            boolean started = false;
            try {
                start0();
                started = true;
            } finally {
                try {
                    if (!started) {
                        group.threadStartFailed(this);
                    }
                } catch (Throwable ignore) {
                }
            }
        }
    
    	// 本地方法启动线程，提交任务给 CPU
        private native void start0();
    
    }

public interface Runnable {
        
        //被实现需要执行的任务
        public abstract void run();
    }

--------------------

### 【Java学习资源】整理推荐 ###

*  [命令模式在开源代码中的应用][Link 1]
 *  [策略模式在开源代码中应用][Link 2]
 *  [模板方法模式在开源代码中应用][Link 3]
 *  [组合模式在开源代码中的应用][Link 4]
 *  [享元模式在开源代码中的应用][Link 5]
 *  [外观模式在开源代码中的应用][Link 6]
 *  [装饰器模式在开源代码中的应用][Link 7]
 *  [桥接模式在开源代码中的应用][Link 8]
 *  [适配器模式在开源代码中的应用][Link 9]
 *  [代理模式在开源代码中的应用][Link 10]
 *  [原型模式在开源代码中的应用][Link 11]
 *  [建造者模式在开源代码中的应用][Link 12]
 *  [工厂模式在开源代码中的应用][Link 13]
 *  [单例模式在开源代码中的应用][Link 14]
 *  [编码规范][Link 15]
 *  [设计模式][Link 16]
 *  [重构][Link 17]
 *  [设计原则][Link 18]
 *  [面向对象到底是什么][Link 19]
 *  [代码质量有哪些评判标准？][Link 20]

--------------------

### 【Java面试题与答案】整理推荐 ###

*  [基础与语法][Link 21]
 *  [集合][Link 22]
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 *  [并发编程][Link 24]
 *  [Web][]
 *  [安全][Link 25]
 *  [设计模式][Link 26]
 *  [框架][Link 27]
 *  [算法与数据结构][Link 28]
 *  [异常][Link 29]
 *  [文件解析与生成][Link 30]
 *  [Linux][]
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 *  [Dubbo][]

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