建造器模式实战（Builder模式）

最近在阅读在Effective Java第三版，其中提到了建造器模式（建造者详解：https://blog.csdn.net/sinat_35821285/article/details/80004060），找了一个实际生产使用的例子。

（当遇到多个构造器参数时要考虑使用建造器模式，即Builder模式。）

1）最常见的字符串建造器：

的

使用：

public class Main { public static void main(String[] args) { var sb = new StringBuilder(1024); sb.append("Mr ") .append("Bob") .append("!") .insert(0, "Hello, "); System.out.println(sb.toString()); } }

2）线程工厂建造者的部分代码，完整代码请看Guava

public final class ThreadFactoryBuilder { // 线程名称前缀 private String nameFormat = null; // 设置通过该线程工厂实例创建的线程是否为守护线程 private Boolean daemon = null; // 设置通过该线程工厂实例创建的线程的优先级: 1~10 private Integer priority = null; // 设置通过该线程工厂实例创建的线程的未捕获异常处理器 private UncaughtExceptionHandler uncaughtExceptionHandler = null; // 设置真实运行的后台线程工厂实例 private ThreadFactory backingThreadFactory = null; public ThreadFactoryBuilder() {} public ThreadFactoryBuilder setName(String name) { this.nameFormat = name + "-%d"; return this; } public ThreadFactoryBuilder setDaemon(boolean daemon) { this.daemon = daemon; return this; } public ThreadFactoryBuilder setPriority(int priority) { this.priority = priority; return this; } public ThreadFactoryBuilder setUncaughtExceptionHandler(UncaughtExceptionHandler uncaughtExceptionHandler) { this.uncaughtExceptionHandler = Verify.notNull(uncaughtExceptionHandler); return this; } public ThreadFactoryBuilder setThreadFactory(ThreadFactory backingThreadFactory) { this.backingThreadFactory = Verify.notNull(backingThreadFactory); return this; } public ThreadFactory build() { return doBuild(this); } // 拆分，以便匿名ThreadFactory不能包含一个可以返回到Builder构造实例的引用。 private static ThreadFactory doBuild(ThreadFactoryBuilder builder) { final String nameFormat = builder.nameFormat; final Boolean daemon = builder.daemon; final Integer priority = builder.priority; final UncaughtExceptionHandler uncaughtExceptionHandler = builder.uncaughtExceptionHandler; final ThreadFactory backingThreadFactory = (builder.backingThreadFactory != null) ? builder.backingThreadFactory : Executors.defaultThreadFactory(); final AtomicLong count = (nameFormat != null) ? new AtomicLong(0) : null; return new ThreadFactory() { @Override public Thread newThread(Runnable runnable) { Thread thread = backingThreadFactory.newThread(runnable); if (nameFormat != null) { thread.setName(format(nameFormat, count.getAndIncrement())); } if (daemon != null) { thread.setDaemon(daemon); } if (priority != null) { thread.setPriority(priority); } if (uncaughtExceptionHandler != null) { thread.setUncaughtExceptionHandler(uncaughtExceptionHandler); } return thread; } }; } }

使用：我们利用建造者可以创建线程池，利用多线程来完成一些任务

public class ThreadFactoryBuilderTest { public static void main(String[] args) { // 创建Task Service service = new Service(); // 线程工厂建造者 ThreadFactory threadFactory = new ThreadFactoryBuilder().setName("test-pool") // 设置使用此ThreadFactory创建的线程时使用的命名前缀 .setDaemon(false) // 设置通过该线程工厂实例创建的线程是否为守护线程 .setPriority(1) // 设置通过该线程工厂实例创建的线程的优先级 // .setThreadFactory(backingThreadFactory) .build(); // 建造者模式完成 ExecutorService pool = Executors.newCachedThreadPool(threadFactory); for (int i = 0; i < 9; i++) { pool.submit(service); } pool.shutdown(); } public static class Service implements Runnable { private static SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS"); public void run() { System.out.println(Thread.currentThread().getName() + ":doSomething start-time:" + sf.format(System.currentTimeMillis())); } } }