需求
需求： 假设有10个线程，最多同时运行5个
要求： 不使用线程池，使用synchronized-wait¬ifyAll机制
实现
详见注释
package com.artisan.test; import java.time.LocalTime; import java.util.*; /** * 需求： 假设有10个线程，最多同时运行5个 * 要求： 不使用线程池，使用synchronized-wait¬ifyAll机制 */ public class ExerciseDemo { // 锁 Monitor private static final LinkedList<Control> CONTROLLIST = new LinkedList(); // 同时运行的最大线程数 private static final int MAX_THREADS = 5; /** * 创建线程 * @param threadName 线程名称 * @return */ public static Thread createWorkThread(String threadName){ return new Thread(() ->{ // 加锁 synchronized (CONTROLLIST){ Optional.of(Thread.currentThread().getName() + " GOT LOCK ,BEGIN..." + LocalTime.now().withNano(0)).ifPresent(System.out::println); // 使用while // 当集合中运行的线程数量大于5时，wait,放弃锁，不执行 while (CONTROLLIST.size() >= MAX_THREADS){ try { Optional.of(Thread.currentThread().getName() + " WAIT").ifPresent(System.out::println); CONTROLLIST.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } // 加入到LinkedList最后 CONTROLLIST.addLast(new Control()); } //模拟每个线程的业务，假设需要10秒才能结束 Optional.of(Thread.currentThread().getName() + " working..." + LocalTime.now().withNano(0)).ifPresent(System.out::println); try { Thread.sleep(10_000); } catch (InterruptedException e) { e.printStackTrace(); } // 输出业务完成 Optional.of(Thread.currentThread().getName() + " END..." + LocalTime.now().withNano(0)).ifPresent(System.out::println); // 加锁 synchronized (CONTROLLIST){ // 移除最上面的线程 CONTROLLIST.removeFirst(); // 唤醒其他所有等待的线程 CONTROLLIST.notifyAll(); } },threadName); } /** * 主流程 * @param args */ public static void main(String[] args) { List<Thread> workers = new ArrayList(); Arrays.asList("T1","T2","T3","T4","T5","T6","T7","T8","T9","T10") .stream() .map(ExerciseDemo::createWorkThread) .forEach(t->{ // 启动线程 t.start(); // 加入到集合列表，待后续一起join workers.add(t); }); // 比那里保存线程的集合，10个线程 join workers.stream().forEach(t -> { try { t.join(); } catch (InterruptedException e) { e.printStackTrace(); } } ); // 全部完成后，输出结束标识 Optional.of("DONE").ifPresent(System.out::println); } /** * 没啥实质做用，仅仅是个控制标识 */ static class Control{ } }
运行日志
"E:\Program Files\Java\jdk1.8.0_161\bin\java" "-javaagent:E:\Program Files\JetBrains\IntelliJ IDEA 2017.2.4\lib\idea_rt.jar=60076:E:\Program Files\JetBrains\IntelliJ IDEA 2017.2.4\bin" -Dfile.encoding=UTF-8 -classpath "E:\Program Files\Java\jdk1.8.0_161\jre\lib\charsets.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\deploy.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\access-bridge-64.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\cldrdata.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\dnsns.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\jaccess.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\jfxrt.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\localedata.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\nashorn.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\sunec.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\sunjce_provider.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\sunmscapi.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\sunpkcs11.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\ext\zipfs.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\javaws.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\jce.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\jfr.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\jfxswt.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\jsse.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\management-agent.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\plugin.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\resources.jar;E:\Program Files\Java\jdk1.8.0_161\jre\lib\rt.jar;D:\IdeaProjects\mvc\target\classes" com.artisan.test.ExerciseDemo T1 GOT LOCK ,BEGIN...00:03:41 T10 GOT LOCK ,BEGIN...00:03:41 T9 GOT LOCK ,BEGIN...00:03:41 T8 GOT LOCK ,BEGIN...00:03:41 T1 working...00:03:41 T7 GOT LOCK ,BEGIN...00:03:41 T8 working...00:03:41 T7 working...00:03:41 T10 working...00:03:41 T9 working...00:03:41 T6 GOT LOCK ,BEGIN...00:03:41 T6 WAIT T5 GOT LOCK ,BEGIN...00:03:41 T5 WAIT T4 GOT LOCK ,BEGIN...00:03:41 T4 WAIT T3 GOT LOCK ,BEGIN...00:03:41 T3 WAIT T2 GOT LOCK ,BEGIN...00:03:41 T2 WAIT T10 END...00:03:51 T8 END...00:03:51 T2 working...00:03:51 T4 WAIT T3 working...00:03:51 T5 WAIT T6 WAIT T1 END...00:03:51 T6 working...00:03:51 T5 WAIT T4 WAIT T9 END...00:03:51 T4 working...00:03:51 T5 WAIT T7 END...00:03:51 T5 working...00:03:51 T2 END...00:04:01 T3 END...00:04:01 T6 END...00:04:01 T4 END...00:04:01 T5 END...00:04:01 DONE Process finished with exit code 0
首先主线程中 初始化10个线程，分别命名为T1 … T10，先把这10个线程临时存放到集合
遍历集合，分别join . 不能在上一步的地方join , 这样的话就只能一个线程 一个线程的执行了（join会阻塞当前线程）
10个线程全部完成后，打印DONE
完成主要部分的编码后，就需要关注thread具体的业务逻辑了 ： 定义一个锁 LinkedList<Control> ，当线程获取到锁，就将Control添加到Monitor中，如果大于规定的线程数，则wait
业务部分并行执行，当一个线程完成后，获取锁，从Monitor中移除一个Control， 然后notifyAll所有正在等待的线程
符合需求 ,OK
