多线程---并发容器的使用

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原创最新推荐文章于 2026-03-06 00:23:40 发布 1.8w 阅读 AI 写同款· GEO 优化 ›

并发容器的原理，7大并发容器详解、及使用场景并发容器的原理，7大并发容器详解、及使用场景 http://youzhixueyuan.com/use-of-concurrent-containers.html 并发容器的由来在Java并发编程中，经常听到Java集合类，同步容器、并发容器，那么他们有哪些具体分类，以及各自之间的区别和优劣呢？只有把这些梳理清楚了，你才能真正掌握在高并发的环境下，正确使用好并发容器，我们先从Java集... 阅读详情

1. 容器概览

在这里插入图片描述

2. 容器的使用

1. Map

多线程环境下，几种Map的处理效率和线程安全问题

测试方案：准备10万条数据， 10个线程，每个线程处理1万条数据，并发执行。

数据准备


public class Constants {
    public static final int COUNT = 1000000;
    public static final int THREAD_COUNT = 100;
}

1. HashTable

HashTable是线程安全的, 因为里面加了很多synchronized, 每次put操作, 都会锁整个Map

public class T01_TestHashtable {

    //HashMap是jdk1.0产生的, 最早出现, 里面的很多方法都加了synchronized锁, 所以效率比较低
    static Hashtable<UUID, UUID> m = new Hashtable<>();

    static int count = Constants.COUNT;
    static UUID[] keys = new UUID[count];
    static UUID[] values = new UUID[count];
    static final int THREAD_COUNT = Constants.THREAD_COUNT;

    //先准备好测试用例, 减少干扰因素
    static {
        for (int i = 0; i < count; i++) {
            keys[i] = UUID.randomUUID();
            values[i] = UUID.randomUUID();
        }
    }

    /**
     * 每个线程处理1万条数据,
     */
    static class MyThread extends Thread {
        int start;
        int gap = count / THREAD_COUNT;

        public MyThread(int start) {
            this.start = start;
        }

        @Override
        public void run() {
            //从start开始, 到start+gap个结束
            for (int i = start; i < start + gap; i++) {
                m.put(keys[i], values[i]);
            }
        }
    }

    public static void main(String[] args) {

        long start = System.currentTimeMillis();

        Thread[] threads = new Thread[THREAD_COUNT];

        for (int i = 0; i < threads.length; i++) {
            //设置每个线程的起始值不一样
            threads[i] =
                    new MyThread(i * (count / THREAD_COUNT));
        }

        for (Thread t : threads) {
            t.start();
        }

        for (Thread t : threads) {
            try {
                //主线程等待每个线程都执行结束
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        long end = System.currentTimeMillis();
        //插入执行的时间
        System.out.println(end - start);

        System.out.println(m.size());

        //-----------------------------------

        start = System.currentTimeMillis();
        for (int i = 0; i < threads.length; i++) {
            threads[i] = new Thread(() -> {
                for (int j = 0; j < 10000000; j++) {
                    m.get(keys[10]);
                }
            });
        }

        for (Thread t : threads) {
            t.start();
        }

        for (Thread t : threads) {
            try {
                //主线程需要等待所有子线程执行完
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        end = System.currentTimeMillis();
        System.out.println(end - start);
    }
}

执行结果

写耗时: 290
1000000
读耗时: 29602

可以看到执行时间在300毫秒左右

2. HashMap

sun在HashTablede的基础上推出了无锁的HashMap

public class T02_TestHashMap {

    //sun在HashTablede的基础上推出了无锁的HashMap
    static HashMap<UUID, UUID> m = new HashMap<>();

    static int count = Constants.COUNT;
    static UUID[] keys = new UUID[count];
    static UUID[] values = new UUID[count];
    static final int THREAD_COUNT = Constants.THREAD_COUNT;

    static {
        for (int i = 0; i < count; i++) {
            keys[i] = UUID.randomUUID();
            values[i] = UUID.randomUUID();
        }
    }

    static class MyThread extends Thread {
        int start;
        int gap = count / THREAD_COUNT;

        public MyThread(int start) {
            this.start = start;
        }

        @Override
        public void run() {
            for (int i = start; i < start + gap; i++) {
                //HashMap在resize(扩容)时, 可能会出现多个线程同时进行, 导致数据丢失甚至死锁情况
                m.put(keys[i], values[i]);
            }
        }
    }

    public static void main(String[] args) {

        long start = System.currentTimeMillis();

        Thread[] threads = new Thread[THREAD_COUNT];

        for (int i = 0; i < threads.length; i++) {
            threads[i] =
                    new MyThread(i * (count / THREAD_COUNT));
        }

        for (Thread t : threads) {
            t.start();
        }

        for (Thread t : threads) {
            try {
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        long end = System.currentTimeMillis();
        System.out.println(end - start);

        System.out.println(m.size());
    }
}

执行结果

写耗时: 171
814683
读耗时: 2005

可以看到即使执行成功, 总数也不是10万条, 因为设计到Map的resize扩容, 多线程环境下, 同时进入扩容操作, 会出现问题, 具体参考: https://www.jianshu.com/p/e2f75c8cce01

3. SynchronizedHashMap

相当于有锁版的HashMap, 锁的粒度比HashTable小了一些


public class T03_TestSynchronizedHashMap {

    //相当于有锁版的HashMap, 锁的粒度比HashTable小了一些
    static Map<UUID, UUID> m = Collections.synchronizedMap(new HashMap<UUID, UUID>());

    static int count = Constants.COUNT;
    static UUID[] keys = new UUID[count];
    static UUID[] values = new UUID[count];
    static final int THREAD_COUNT = Constants.THREAD_COUNT;

    static {
        for (int i = 0; i < count; i++) {
            keys[i] = UUID.randomUUID();
            values[i] = UUID.randomUUID();
        }
    }

    static class MyThread extends Thread {
        int start;
        int gap = count / THREAD_COUNT;

        public MyThread(int start) {
            this.start = start;
        }

        @Override
        public void run() {
            for (int i = start; i < start + gap; i++) {
                m.put(keys[i], values[i]);
            }
        }
    }

    public static void main(String[] args) {

        long start = System.currentTimeMillis();

        Thread[] threads = new Thread[THREAD_COUNT];

        for (int i = 0; i < threads.length; i++) {
            threads[i] =
                    new MyThread(i * (count / THREAD_COUNT));
        }

        for (Thread t : threads) {
            t.start();
        }

        for (Thread t : threads) {
            try {
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        long end = System.currentTimeMillis();
        System.out.println(end - start);

        System.out.println(m.size());

        //-----------------------------------

        start = System.currentTimeMillis();
        for (int i = 0; i < threads.length; i++) {
            threads[i] = new Thread(() -> {
                for (int j = 0; j < 10000000; j++) {
                    m.get(keys[10]);
                }
            });
        }

        for (Thread t : threads) {
            t.start();
        }

        for (Thread t : threads) {
            try {
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        end = System.currentTimeMillis();
        System.out.println(end - start);
    }
}

执行结果

写耗时: 334
1000000
读耗时: 29575

4. ConcurrentHashMap

ConcurrentHashMap并发插入的时候, 效率未必比其他Map高, 但是并发读取的时候效率很

/**
 * ConcurrentHashMap并发插入的时候, 效率未必比其他Map高, 但是并发读取的时候效率很高
 */
public class T04_TestConcurrentHashMap {

    //结合了JUC包里的一些锁
    static Map<UUID, UUID> m = new ConcurrentHashMap<>();

    static int count = Constants.COUNT;
    static UUID[] keys = new UUID[count];
    static UUID[] values = new UUID[count];
    static final int THREAD_COUNT = Constants.THREAD_COUNT;

    static {
        for (int i = 0; i < count; i++) {
            keys[i] = UUID.randomUUID();
            values[i] = UUID.randomUUID();
        }
    }

    static class MyThread extends Thread {
        int start;
        int gap = count/THREAD_COUNT;

        public MyThread(int start) {
            this.start = start;
        }

        @Override
        public void run() {
            for(int i=start; i<start+gap; i++) {
                m.put(keys[i], values[i]);
            }
        }
    }

    public static void main(String[] args) {

        long start = System.currentTimeMillis();

        Thread[] threads = new Thread[THREAD_COUNT];

        for(int i=0; i<threads.length; i++) {
            threads[i] =
            new MyThread(i * (count/THREAD_COUNT));
        }

        for(Thread t : threads) {
            t.start();
        }

        for(Thread t : threads) {
            try {
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        long end = System.currentTimeMillis();
        System.out.println("写耗时: " + (end - start));

        System.out.println(m.size());

        //-----------------------------------

        start = System.currentTimeMillis();
        for (int i = 0; i < threads.length; i++) {
            threads[i] = new Thread(()->{
                for (int j = 0; j < 10000000; j++) {
                    m.get(keys[10]);
                }
            });
        }

        for(Thread t : threads) {
            t.start();
        }

        for(Thread t : threads) {
            try {
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        end = System.currentTimeMillis();
        System.out.println("读耗时: " + (end - start));
    }
}

写耗时: 160
1000000
读耗时: 1108

2. Collection

多线程环境下集合的使用, 由一个测试题引入

测试题:

有N张火车票，每张票都有一个编号
同时有10个窗口对外售票
请写一个模拟程序

1. ArrayList

/**
 * 有N张火车票，每张票都有一个编号
 * 同时有10个窗口对外售票
 * 请写一个模拟程序
 *
 * 分析下面的程序可能会产生哪些问题？
 * 重复销售？超量销售？
 *
 *
 * @author cyc
 */
package com.cyc.juc.c_024_FromVectorToQueue;

import java.util.ArrayList;
import java.util.List;

public class TicketSeller1ArrayList {
    static List<String> tickets = new ArrayList<>();

    static {
        for (int i = 0; i < 10000; i++) {
            //提前将票添加到集合中
            tickets.add("票编号：" + i);
        }
    }


    public static void main(String[] args) {
        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                while (tickets.size() > 0) {
                    //有可能只剩了一张票, 但是多个线程都通过了这个判断, 然后多线程直接开始remove, 所以会导致超卖的情况
                    System.out.println("销售了--" + tickets.remove(0));
                }
            }).start();
        }
    }
}

执行结果

Exception in thread “Thread-7” java.lang.ArrayIndexOutOfBoundsException: -1
at java.util.ArrayList.remove(ArrayList.java:505)
at com.cyc.juc.c_024_FromVectorToQueue.TicketSeller1ArrayList.lambda$main$0(TicketSeller1ArrayList.java:32)
at java.lang.Thread.run(Thread.java:748)

最后多个线程都进入了判断, 并开始卖最后一张票, 导致数组越界异常。

Queue和List对比

Queue中提供了一些对线程友好的API offer, peek, poll

BlockingQueue

中的put方法和take方法可实现线程堵塞

2. Vector

/**
 * 有N张火车票，每张票都有一个编号
 * 同时有10个窗口对外售票
 * 请写一个模拟程序
 *
 * 分析下面的程序可能会产生哪些问题？
 *
 * 使用Vector或者Collections.synchronizedXXX
 * 分析一下，这样能解决问题吗？
 *
 * @author cyc
 */
package com.cyc.juc.c_024_FromVectorToQueue;

import java.util.Vector;
import java.util.concurrent.TimeUnit;

public class TicketSeller2Vector {
    static Vector<String> tickets = new Vector<>();


    static {
        for (int i = 0; i < 1000; i++) {
            tickets.add("票 编号：" + i);
        }
    }

    public static void main(String[] args) {

        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                while (tickets.size() > 0) {
                    System.out.println("销售了--" + tickets.remove(0));
                }
            }).start();
        }
    }
}

执行结果可以正常输出

但是如果在

while (tickets.size() > 0) {
                    System.out.println("销售了--" + tickets.remove(0));
                }

之中还有其他业务逻辑需要执行, 假设执行10毫秒, 即代码如下

while (tickets.size() > 0) {
    //所谓的线程安全 , 是调用size()和remove()方法时加锁了, 但是在执行完size()之前和remove()之后, 并没有加锁,
    //这个过程就不是原子的
    try {
        TimeUnit.MILLISECONDS.sleep(10);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }


    System.out.println("销售了--" + tickets.remove(0));
}

输出结果

Exception in thread "Thread-9" java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 0
	at java.util.Vector.remove(Vector.java:834)
	at com.cyc.juc.c_024_FromVectorToQueue.TicketSeller2Vector.lambda$main$0(TicketSeller2Vector.java:42)
	at java.lang.Thread.run(Thread.java:748)

同样导致数据越界异常, 因为Vector的size和remove操作执行过程中不是原子的

优化

给tickets加锁, 并在代码中判断tickets.size()是否等于0


package com.cyc.juc.c_024_FromVectorToQueue;

import java.util.Vector;
import java.util.concurrent.TimeUnit;

public class TicketSeller2Vector {
    static Vector<String> tickets = new Vector<>();


    static {
        for (int i = 0; i < 1000; i++) {
            tickets.add("票 编号：" + i);
        }
    }

    public static void main(String[] args) {

        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                while (tickets.size() > 0) {
                    synchronized (tickets) {
                        //所谓的线程安全 , 是调用size()和remove()方法时加锁了, 但是在执行完size()之前和remove()之后, 并没有加锁,
                        //这个过程就不是原子的

                        if (tickets.size() <= 0) {
                            break;
                        }

                        try {
                            TimeUnit.MILLISECONDS.sleep(10);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }


                        System.out.println("销售了--" + tickets.remove(0));
                    }
                }
            }).start();
        }
    }
}

3. LinkedList

/**
 * 有N张火车票，每张票都有一个编号
 * 同时有10个窗口对外售票
 * 请写一个模拟程序
 *
 * 分析下面的程序可能会产生哪些问题？
 * 重复销售？超量销售？
 *
 * 使用Vector或者Collections.synchronizedXXX
 * 分析一下，这样能解决问题吗？
 *
 * 就算操作A和B都是同步的，但A和B组成的复合操作也未必是同步的，仍然需要自己进行同步
 * 就像这个程序，判断size和进行remove必须是一整个的原子操作
 *
 * @author cyc
 */
package com.cyc.juc.c_024_FromVectorToQueue;

import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.TimeUnit;

public class TicketSeller3VoctorWithSynchronize {
    static List<String> tickets = new LinkedList<>();


    static {
        for (int i = 0; i < 1000; i++) {
            tickets.add("票 编号：" + i);
        }
    }

    public static void main(String[] args) {

        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                while (true) {
                    //给tickets对象加锁, 保证原子性, 实现线程安全
                    synchronized (tickets) {
                        if (tickets.size() <= 0) {
                            break;
                        }

                        try {
                            TimeUnit.MILLISECONDS.sleep(10);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }

                        System.out.println("销售了--" + tickets.remove(0));
                    }
                }
            }).start();
        }
    }
}

4. ConcurrentLinkedQueue

/**
 * 有N张火车票，每张票都有一个编号
 * 同时有10个窗口对外售票
 * 请写一个模拟程序
 *
 * 分析下面的程序可能会产生哪些问题？
 * 重复销售？超量销售？
 *
 * 使用Vector或者Collections.synchronizedXXX
 * 分析一下，这样能解决问题吗？
 *
 * 就算操作A和B都是同步的，但A和B组成的复合操作也未必是同步的，仍然需要自己进行同步
 * 就像这个程序，判断size和进行remove必须是一整个的原子操作
 *
 * 使用ConcurrentQueue提高并发性
 *
 * @author cyc
 */
public class TicketSeller4ConcurrentLinkedQueue {
    //多线程的程序应多考虑使用队列
    static Queue<String> tickets = new ConcurrentLinkedQueue<>();


    static {
        for (int i = 0; i < 1000; i++) {
            tickets.add("票 编号：" + i);
        }
    }

    public static void main(String[] args) {

        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                while (true) {
                    String s = tickets.poll();
                    if (s == null) {
                        break;
                    } else {
                        System.out.println("销售了--" + s);
                    }
                }
            }).start();
        }
    }
}

执行结果正常, 并且速度也很快

3. 并发容器的使用

1. ConcurrentHashMap

/**
 * 几种并发容器Map的使用
 * ConcurrentSkipListMap参考 https://blog.youkuaiyun.com/sunxianghuang/article/details/52221913
 */
public class T01_ConcurrentMap {
    public static void main(String[] args) {
        Map<String, String> map = new ConcurrentHashMap<>();//高并发无序
//    Map<String, String> map = new ConcurrentSkipListMap<>(); //高并发并且排序
        

        //Map<String, String> map = new Hashtable<>();
        //Map<String, String> map = new HashMap<>(); //Collections.synchronizedXXX
        //TreeMap
        Random r = new Random();
        Thread[] threads = new Thread[100];
        //倒数门栓
        CountDownLatch latch = new CountDownLatch(threads.length);
        long start = System.currentTimeMillis();
        //100个线程并发往map里各写入10000条数据
        for (int i = 0; i < threads.length; i++) {
            threads[i] = new Thread(() -> {
                for (int j = 0; j < 10000; j++) {
                    map.put("a" + r.nextInt(100000), "a" + r.nextInt(100000));
//             map.put("a" + m.getAndIncrement(), "a" + m.getAndIncrement());
                }
                latch.countDown();
            });
        }

        Arrays.asList(threads).forEach(t -> t.start());
        try {
            latch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        long end = System.currentTimeMillis();
        System.out.println(end - start);
        System.out.println(map.size());

    }
}

2. CopyOnWriteArrayList

/**
 * 写时复制容器 copy on write
 * 多线程环境下，写时效率低，读时效率高
 * 适合写少读多的环境
 * 因为每次写的时候都要复制一份,
 * 
 * @author cyc
 */
package com.cyc.juc.c_025;

import java.util.Arrays;
import java.util.List;
import java.util.Random;
import java.util.Vector;
import java.util.concurrent.CopyOnWriteArrayList;

public class T02_CopyOnWriteList {
   public static void main(String[] args) {
      List<String> lists = 
//          new ArrayList<>(); //这个会出并发问题！
//          new Vector();
            new CopyOnWriteArrayList<>();//写的时候加锁, 读的时候不加锁
      Random r = new Random();
      Thread[] threads = new Thread[100];
      
      for(int i=0; i<threads.length; i++) {
         Runnable task = new Runnable() {
   
            @Override
            public void run() {
               for(int i=0; i<1000; i++) {
                  lists.add("a" + r.nextInt(10000));
               }
            }
            
         };
         threads[i] = new Thread(task);
      }
      
      //写操作
      runAndWriteComputeTime(threads);

      for(int i=0; i<threads.length; i++) {
         Runnable task = () -> {
            for (String list : lists) {
               String s = list;
            }
         };
         threads[i] = new Thread(task);
      }
      //读操作
      runAndReadComputeTime(threads);

      
      System.out.println("list大小: "+lists.size());
   }

   private static void runAndReadComputeTime(Thread[] threads) {
      long s1 = System.currentTimeMillis();
      Arrays.asList(threads).forEach(t->t.start());
      Arrays.asList(threads).forEach(t->{
         try {
            //主线程等待所有线程执行完
            t.join();
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      });
      long s2 = System.currentTimeMillis();
      System.out.println("读耗时: "+(s2 - s1));
   }

   static void runAndWriteComputeTime(Thread[] threads) {
      long s1 = System.currentTimeMillis();
      Arrays.asList(threads).forEach(t->t.start());
      Arrays.asList(threads).forEach(t->{
         try {
            //主线程等待所有线程执行完
            t.join();
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      });
      long s2 = System.currentTimeMillis();
      System.out.println("写耗时: "+(s2 - s1));
      
   }
}

先来测试同样为线程安全的collection容器Vector

输出结果

写耗时: 86
读耗时: 401
list大小: 100000

测试CopyOnWriteArrayList

输出结果

写耗时: 2769
读耗时: 41
list大小: 100000

可以看到CopyOnWriteArrayList写操作比较慢, 这正是由于每次写入都要进行复制操作 , 但是读数据非常快。

3. ConcurrentLinkedQueue

package com.cyc.juc.c_025;

import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;

/**
 * ConcurrentLinkedQueue并发队列, 先进先出
 */
public class T04_ConcurrentQueue {
   public static void main(String[] args) {
      Queue<String> strs = new ConcurrentLinkedQueue<>();
      
      for(int i=0; i<10; i++) {
         strs.offer("a" + i);  //add
      }
      
      System.out.println(strs);
      
      System.out.println(strs.size());
      //poll取出, 并删除一个
      System.out.println(strs.poll());
      System.out.println(strs.size());

      //peak 取出 , 不删除
      System.out.println(strs.peek());
      System.out.println(strs.size());

   }
}

输出结果

[a0, a1, a2, a3, a4, a5, a6, a7, a8, a9]
10
a0
9
a1
9

4. LinkedBlockingQueue

LinkedBlockingQueue中的锁是分离的，生产者的锁PutLock，消费者的锁takeLock
LinkedBlockingQueue内部维护的是一个链表结构
在生产和消费的时候，需要创建Node对象进行插入或移除，大批量数据的系统中，其对于GC的压力会比较大
LinkedBlockingQueue有默认的容量大小为：Integer.MAX_VALUE，当然也可以传入指定的容量大小

代码演示

/**
 * BlockingQueue天生的阻塞队列
 */
public class T05_LinkedBlockingQueue {

   //
   static BlockingQueue<String> strs = new LinkedBlockingQueue<>();

   static Random r = new Random();

   public static void main(String[] args) {
      new Thread(() -> {
         for (int i = 0; i < 100; i++) {
            try {
               strs.put("a" + i); //如果满了，就会等待
               TimeUnit.MILLISECONDS.sleep(r.nextInt(1000));
            } catch (InterruptedException e) {
               e.printStackTrace();
            }
         }
      }, "p1").start();

      for (int i = 0; i < 5; i++) {
         new Thread(() -> {
            for (;;) {
               try {
                  System.out.println(Thread.currentThread().getName() + " take -" + strs.take()); //如果空了，就会等待
               } catch (InterruptedException e) {
                  e.printStackTrace();
               }
            }
         }, "c" + i).start();

      }
   }
}

5. ArrayBlockingQueue

ArrayBlockingQueue生产者和消费者使用的是同一把锁
ArrayBlockingQueue内部维护了一个数组

在生产和消费的时候，是直接将枚举对象插入或移除的，不会产生或销毁任何额外的对象实例

插入操作
ArrayBlockingQueue在初始化的时候，必须传入一个容量大小的值

在这里插入图片描述

6. DelayQueue

package com.cyc.juc.c_025;

import java.util.Random;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.DelayQueue;
import java.util.concurrent.Delayed;
import java.util.concurrent.TimeUnit;

/**
 * 按照等待时间长短排序执行 , 可以自定义执行优先级
 * 用户: 按照时间进行调度,
 */
public class T07_DelayQueue {

    static BlockingQueue<MyTask> tasks = new DelayQueue<>();

    static Random r = new Random();

    static class MyTask implements Delayed {
        String name;
        long runningTime;

        MyTask(String name, long rt) {
            this.name = name;
            this.runningTime = rt;
        }

        @Override
        public int compareTo(Delayed o) {
            if (this.getDelay(TimeUnit.MILLISECONDS) < o.getDelay(TimeUnit.MILLISECONDS)) {
                return -1;
            } else if (this.getDelay(TimeUnit.MILLISECONDS) > o.getDelay(TimeUnit.MILLISECONDS)) {
                return 1;
            } else {
                return 0;
            }
        }

        @Override
        public long getDelay(TimeUnit unit) {

            return unit.convert(runningTime - System.currentTimeMillis(), TimeUnit.MILLISECONDS);
        }


        @Override
        public String toString() {
            return name + " " + runningTime;
        }
    }

    public static void main(String[] args) throws InterruptedException {
        long now = System.currentTimeMillis();
        MyTask t1 = new MyTask("t1", now + 1000);
        MyTask t2 = new MyTask("t2", now + 2000);
        MyTask t3 = new MyTask("t3", now + 1500);
        MyTask t4 = new MyTask("t4", now + 2500);
        MyTask t5 = new MyTask("t5", now + 500);

        tasks.put(t1);
        tasks.put(t2);
        tasks.put(t3);
        tasks.put(t4);
        tasks.put(t5);

        System.out.println(tasks);

        for (int i = 0; i < 5; i++) {
            System.out.println(tasks.take());
        }
    }
}

7. SynchronousQueue

/**
 * 容量为0
 * SynchronousQueue 同步Queue
 * 常用作一个线程给另一个容器下单任务
 * @author fei
 */
public class T08_SynchronusQueue { //容量为0
   public static void main(String[] args) throws InterruptedException {
      BlockingQueue<String> strs = new SynchronousQueue<>();
      
      new Thread(()->{
         try {
            System.out.println(strs.take());
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      }).start();

      strs.put("aaa"); //阻塞等待消费者消费
      //必须有消费者进行消费才可以继续put,如果没有消费者, 则这里就会堵塞在这里
//    strs.put("bbb");
      //strs.add("aaa");
      System.out.println(strs.size());
   }
}

8. LinkedTransferQueue

package com.cyc.juc.c_025;

import java.util.concurrent.LinkedTransferQueue;

/**
 * 给线程传递任务
 * 用于需要得到执行结果, 才能继续往下执行, 类似MQ的一个返回处理结果机制
 * @author cyc
 */
public class T09_TransferQueue {
   public static void main(String[] args) throws InterruptedException {
      LinkedTransferQueue<String> strs = new LinkedTransferQueue<>();
      
      new Thread(() -> {
         try {
            System.out.println(strs.take());
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      }).start();
      //和put的区别在于, 线程put完之后, 执行put的线程就可以走了,
      // 而transfer, 执行transfer的线程必须原地等着, 阻塞住, 直到有线程取走transfer的值才行
      //put是满了才等着, transfer是来了就得等着
      strs.transfer("aaa");
      
      //strs.put("aaa");


      /*new Thread(() -> {
         try {
            System.out.println(strs.take());
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
      }).start();*/


   }
}

3. 练习题

要求用线程顺序打印A1B2C3…Z26

1. 使用LockSupport

/**
 * Locksupport park 当前线程阻塞（停止）
 * unpark(Thread t)
 */
public class T02_00_LockSupport {


    static Thread t1 = null, t2 = null;

    public static void main(String[] args) throws Exception {
        char[] aC = "ABCDEFG".toCharArray();
        char[] aI = "1234567".toCharArray();

        t1 = new Thread(() -> {

            for(char c : aC) {
                System.out.print(c);
                LockSupport.unpark(t2); //叫醒t2
                LockSupport.park(); //t1阻塞
            }
        }, "t1");

        t2 = new Thread(() -> {
            for(char c : aI) {
                //保证t1先执行
                LockSupport.park(); //T2阻塞
                System.out.print(c);
                LockSupport.unpark(t1); //叫醒T1
            }
        }, "t2");

        t1.start();
        t2.start();
    }
}

输出结果

A1B2C3D4E5F6G7

2. 使用synchronized, notify,wait

public class T06_00_sync_wait_notify {
    public static void main(String[] args) {
        //新建一个需要被锁的对象
        final Object o = new Object();

        char[] aI = "1234567".toCharArray();
        char[] aC = "ABCDEFG".toCharArray();

        new Thread(()->{
            synchronized (o) {
                for(char c : aI) {
                    System.out.print(c);
                    try {
                        o.notify();//叫醒第二个线程
                        //这里为什么使用wait而不是sleep, wait可以释放锁, sleep不会释放锁
                        o.wait(); //让出锁
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                //必须，否则无法停止程序, 因为两个线程最后会有一个是wait状态,
                // 如果不进行o.notify(),则无法叫醒那个wait()的线程
                o.notify();
            }

        }, "t1").start();

        new Thread(()->{
            synchronized (o) {
                for(char c : aC) {
                    System.out.print(c);
                    try {
                        o.notify();
                        o.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }

                o.notify();
            }
        }, "t2").start();
    }
}

保证执行顺序 , 先打印A, 再打印1, 然后依次B,2,C,3…

使用CountDownLatch保证顺序

package com.cyc.juc.c_026_00_interview.A1B2C3;


import java.util.concurrent.CountDownLatch;

/**
 * 多线程保证执行顺序, 使A先输出, 再输出1
 */
public class T07_00_sync_wait_notify_sort {

    private static CountDownLatch latch = new CountDownLatch(1);

    public static void main(String[] args) {
        final Object o = new Object();



        char[] aI = "1234567".toCharArray();
        char[] aC = "ABCDEFG".toCharArray();

        new Thread(()->{
            try {
                latch.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (o) {

                for(char c : aI) {
                    System.out.print(c);
                    try {
                        //唤醒第二个线程
                        o.notify();
                        //让出锁
                        o.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }

                o.notify();
            }
        }, "t1").start();

        new Thread(()->{

            synchronized (o) {
                for(char c : aC) {
                    System.out.print(c);
                    //输出之后, 进行减1
                    latch.countDown();
                    try {
                        //唤醒第一个线程
                        o.notify();
                        //让出锁
                        o.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                o.notify();
            }
        }, "t2").start();
    }
}

使用volatile+标识字段

package com.cyc.juc.c_026_00_interview.A1B2C3;


import java.util.concurrent.CountDownLatch;

/**
 * 多线程保证执行顺序, 使A先输出, 再输出1
 */
public class T07_00_sync_wait_notify_sort {

    private static volatile boolean t2Started = false;

    public static void main(String[] args) {
        final Object o = new Object();



        char[] aI = "1234567".toCharArray();
        char[] aC = "ABCDEFG".toCharArray();

        new Thread(()->{
            synchronized (o) {

                while(!t2Started) {
                    try {
                        o.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }

                for(char c : aI) {
                    System.out.print(c);
                    try {
                        //唤醒第二个线程
                        o.notify();
                        //让出锁
                        o.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }

                o.notify();
            }
        }, "t1").start();

        new Thread(()->{

            synchronized (o) {
                for(char c : aC) {
                    System.out.print(c);
                    t2Started = true;
                    try {
                        //唤醒第一个线程
                        o.notify();
                        //让出锁
                        o.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                o.notify();
            }
        }, "t2").start();
    }
}

3. 使用Lock.newCondition()

/**
 * 使用lock.newCondition()创建等待队列
 * @author cyc
 */
public class T08_00_lock_condition {

    public static void main(String[] args) {

        char[] aI = "1234567".toCharArray();
        char[] aC = "ABCDEFG".toCharArray();

        Lock lock = new ReentrantLock();
        Condition condition = lock.newCondition();

        new Thread(()->{
            try {
                lock.lock();

                for(char c : aI) {
                    System.out.print(c);
                    //唤醒一个等待在condition上的线程，将该线程从等待队列中转移到同步队列中
                    condition.signal();
                    //当前线程进入等待状态
                    condition.await();
                }

                condition.signal();

            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "t1").start();

        new Thread(()->{
            try {
                lock.lock();

                for(char c : aC) {
                    System.out.print(c);
                    condition.signal();
                    condition.await();
                }

                condition.signal();

            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "t2").start();
    }
}

优化

/**
 * Condition本质是锁资源上不同的等待队列
 */
public class T09_00_lock_condition_two {

    public static void main(String[] args) {

        char[] aI = "1234567".toCharArray();
        char[] aC = "ABCDEFG".toCharArray();

        Lock lock = new ReentrantLock();
        //condition实际上是一个等待队列
        Condition conditionT1 = lock.newCondition();
        Condition conditionT2 = lock.newCondition();

        new Thread(()->{
            try {
                lock.lock();

                for(char c : aI) {
                    System.out.print(c);
                    conditionT2.signal();
                    conditionT1.await();
                }

                conditionT2.signal();

            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "t1").start();

        new Thread(()->{
            try {
                lock.lock();

                for(char c : aC) {
                    System.out.print(c);
                    conditionT1.signal();
                    conditionT2.await();
                }

                conditionT1.signal();

            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }, "t2").start();
    }
}

4. 使用Exchanger

package com.cyc.juc.c_026_00_interview.A1B2C3;

import java.util.concurrent.Exchanger;

public class T12_00_Exchanger_Not_Work {
    private static Exchanger<String> exchanger = new Exchanger<>();

    public static void main(String[] args) {
        char[] aI = "1234567".toCharArray();
        char[] aC = "ABCDEFG".toCharArray();

        new Thread(()->{
            for(int i=0; i<aI.length; i++) {
                System.out.print(aI[i]);
                try {
                    //Exchanger类中的exchange(String x) 方法具有阻塞的特点，也就是说此方法被调用后等待其他线程来获取数据，
                    // 如果没有其他线程取得数据，则就会一直阻塞等待下去。
                    exchanger.exchange("T1");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();

        new Thread(()->{
            for(int i=0; i<aC.length; i++) {
                try {
                    exchanger.exchange("T2");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.print(aC[i]);
            }
        }).start();
    }
}

5. 使用TransferQueue队列

package com.cyc.juc.c_026_00_interview.A1B2C3;

import java.util.concurrent.LinkedTransferQueue;
import java.util.concurrent.TransferQueue;

/**
 * TransferQueue
 */
public class T13_TransferQueue {
    public static void main(String[] args) {
        char[] aI = "1234567".toCharArray();
        char[] aC = "ABCDEFG".toCharArray();

        TransferQueue<Character> queue = new LinkedTransferQueue<>();
        new Thread(()->{
            try {
                for (char c : aI) {
                    //第一个线程作为消费者,去take , 如果没有, 则等待
                    System.out.print(queue.take());
                    queue.transfer(c);
                }

            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "t1").start();

        new Thread(()->{
            try {
                for (char c : aC) {
                    //将c交给对方去打印
                    queue.transfer(c);
                    System.out.print(queue.take());
                }

            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "t2").start();
    }
}

6. 使用CAS-1

package com.cyc.juc.c_026_00_interview.A1B2C3;


public class T03_00_cas {

    enum ReadyToRun {T1, T2}

    //保证线程之间的可见性, 当r有改动时, 可以立即通知其他线程进行更新缓存
    static volatile ReadyToRun r = ReadyToRun.T1; 

    public static void main(String[] args) {

        char[] aC = "ABCDEFG".toCharArray();
        char[] aI = "1234567".toCharArray();

        new Thread(() -> {

            for (char c : aC) {
                while (r != ReadyToRun.T1) {}
                System.out.print(c);
                r = ReadyToRun.T2;
            }

        }, "t1").start();

        new Thread(() -> {

            for (char c : aI) {
                while (r != ReadyToRun.T2) {}
                System.out.print(c);
                r = ReadyToRun.T1;
            }
        }, "t2").start();
    }
}

7. 使用CAS-2

package com.cyc.juc.c_026_00_interview.A1B2C3;


import java.util.concurrent.atomic.AtomicInteger;

public class T05_00_AtomicInteger {

    static AtomicInteger threadNo = new AtomicInteger(1);


    public static void main(String[] args) {

        char[] aI = "1234567".toCharArray();
        char[] aC = "ABCDEFG".toCharArray();


        new Thread(() -> {

            for (char c : aI) {
                while (threadNo.get() != 1) {}
                System.out.print(c);
                threadNo.set(2);
            }

        }, "t1").start();

        new Thread(() -> {

            for (char c : aC) {
                while (threadNo.get() != 2) {}
                System.out.print(c);
                threadNo.set(1);
            }
        }, "t2").start();
    }
}

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