异步线程编程，线程池，线程组，后面涉及ThreadLocal在理解

join模拟订单

package com.future.demo.future;

/**
 * 
 * 
 * @author Administrator
 *
 */
public class NormalThreadTest {
    
    public static void main(String[] args) throws Exception {
        long start = System.currentTimeMillis();
        // 开启购买厨具线程
        ShoppingThread shopping = new ShoppingThread();
        shopping.start();
        shopping.join(); // 保障厨具购买并送货
        // 获取到购买厨具
        KitchenWare kc = shopping.kc;
        
        // 买食材
        FoodMaterial fm = new FoodMaterial();
        Thread.sleep(2000);
        System.out.println("第二步: 食材已经到位");
        // 烹饪美食
        cooking(kc, fm);
        System.out.println("第三步: 美食烹饪完成");
        long end = System.currentTimeMillis();
        System.out.println("烹饪美食时间为:" +  (end - start));
    }
    
    
    /**
     * 定义网上购物厨具线程
     * @author Administrator
     *
     */
    static class ShoppingThread extends Thread {
        
        // 厨具对象引用
        private KitchenWare kc;
        
        @Override
        public void run() {
            System.out.println("第一步: 网上下单");
            System.out.println("第一步: 等待厨具");
            try {
                Thread.sleep(5000); // 等待厨具时间
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("第一步: 快递送货");
            // 生产厨具
            kc = new KitchenWare();
        }
    }
    
    /**
     * 厨具类
     * @author Administrator
     *
     */
    static class KitchenWare {
        
    }
    
    /**
     * 食材类
     * @author Administrator
     *
     */
    static class FoodMaterial {
        
    }
    
    /**
     * 定义烹饪食物的方法
     * @param kc
     * @param fm
     */
    static void cooking(KitchenWare kc, FoodMaterial fm) {
        
    }
}
异步进行
package com.future.demo.future;

import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;

/**
 * 异步: 同时进行
 * 同步: 排队进行
 * @author Administrator
 *
 */
public class FutureThreadTest {
    
    
    public static void main(String[] args) throws Exception {
        long start = System.currentTimeMillis();
        
        Callable<KitchenWare> callable = new Callable<KitchenWare>() {
            public KitchenWare call() throws Exception {
                System.out.println("第一步: 网上下单");
                System.out.println("第一步: 等待厨具");
                try {
                    Thread.sleep(5000); // 等待厨具时间
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("第一步: 快递送货");
                return new KitchenWare();
            }
            
        };
        // 包装为异步执行的对象
        FutureTask<KitchenWare> task = new FutureTask<>(callable);
        new Thread(task).start();
        
        // 买食材
        FoodMaterial fm = new FoodMaterial();
        Thread.sleep(2000);
        System.out.println("第二步: 食材已经到位");
        
        if (!task.isDone()) {
            System.out.println("厨具还没有到.....");
        }
        // 通过阻塞形式获取到异步块执行的结果
        KitchenWare kc = task.get(); // 阻塞
        // 烹饪美食
        cooking(kc, fm);
        System.out.println("第三步: 美食烹饪完成");
        long end = System.currentTimeMillis();
        System.out.println("烹饪美食时间为:" +  (end - start));
    }
    
    
    /**
     * 厨具类
     * @author Administrator
     *
     */
    static class KitchenWare {
        
    }
    
    /**
     * 食材类
     * @author Administrator
     *
     */
    static class FoodMaterial {
        
    }
    
    /**
     * 定义烹饪食物的方法
     * @param kc
     * @param fm
     */
    static void cooking(KitchenWare kc, FoodMaterial fm) {
        
    }
}

 线程池

ThreadPoolExecutor
package com.future.demo.threadPool;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**
 * ThreadPoolExecutor
 *  int corePoolSize 线程总数 <= 最大线程数  
 *  int maximumPoolSize 最大线程数  
 *  long keepAliveTime 存活时间 
 *  TimeUnit unit 时间单位 (纳秒，毫秒，秒，分钟,....)
 *  BlockingQueue<Runnable> workQueue 阻塞队列
 * @author Administrator
 *
 */
public class ThreadPoolExecutorTest {
    public static void main(String[] args) {
        // 20来源: 最大线程数  + 阻塞数目
        ThreadPoolExecutor executor = 
                new ThreadPoolExecutor(10, 30, 2000, TimeUnit.MILLISECONDS, new ArrayBlockingQueue<>(10));
        
        for ( int i = 0; i < 40; i++) {
            executor.execute(new MyRunnable());
            System.out.println("线程池中线程数目：" + executor.getPoolSize() + "，队列中等待执行的任务数目：" + executor.getQueue().size()
                    + "，任务总数目：" + executor.getTaskCount());
        }
        
        // 防止线程溢出(执行完成的线程会被及时关闭)
        executor.shutdownNow();
    }
    
    static class MyRunnable implements Runnable {
        public void run() {
            String threadName = Thread.currentThread().getName();
            System.out.println(threadName+ "准备执行......");
            /*try {
                // jdk1.5 之后官方推荐使用此方法睡眠
                TimeUnit.MILLISECONDS.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }*/
            System.out.println(threadName+"执行完成......");
            
        }
    }
}

  SingleThreadExecutor

package com.future.demo.threadPool;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
 * 创建一个单线程的线程池。这个线程池只有一个线程在工作，
 * 也就是相当于单线程串行执行所有任务。如果这个唯一的线程因为异常结束，
 * 那么会有一个新的线程来替代它。此线程池保证所有任务的执行顺序按照任务的提交顺序执行。
 * @author Administrator
 *
 */
public class SingleThreadExecutorTest {
    
    public static void main(String[] args) {
        MyThread t1 = new MyThread("AAA");
        MyThread t2 = new MyThread("BBB");
        MyThread t3 = new MyThread("CCC");
        MyThread t4 = new MyThread("DDD");
        
        ExecutorService singleThreadExecutor = Executors.newSingleThreadExecutor();
        // 保证在线程池中的线程执行的顺序
        singleThreadExecutor.execute(t4);
        singleThreadExecutor.execute(t1);
        singleThreadExecutor.execute(t2);
        singleThreadExecutor.execute(t3);
        
        singleThreadExecutor.shutdown();
    }
    

}

class MyThread extends Thread {
    private String name;
    public MyThread(String name) {
        super(name);
        this.name = name;
    }

    @Override
    public void run() {
        System.out.println(name+"执行");
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}
FixedThreadExecutor
package com.future.demo.threadPool;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
 * 创建固定大小的线程池。每次提交一个任务就创建一个线程，直到线程达到线程池的最大大小。
 * 线程池的大小一旦达到最大值就会保持不变，
 * 如果某个线程因为执行异常而结束，那么线程池会补充一个新线程。
 * @author Administrator
 *
 */
public class FixedThreadExecutorTest {
    
    public static void main(String[] args) {
        MyThread t1 = new MyThread("AAA");
        MyThread t2 = new MyThread("BBB");
        MyThread t3 = new MyThread("CCC");
        MyThread t4 = new MyThread("DDD");
        
        ExecutorService singleThreadExecutor = Executors.newFixedThreadPool(2);
        
        singleThreadExecutor.execute(t1);
        singleThreadExecutor.execute(t2);
        singleThreadExecutor.execute(t3);
        singleThreadExecutor.execute(t4);
        
        singleThreadExecutor.shutdown();
    }
    

}
CacheThreadExecutor
package com.future.demo.threadPool;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
 * 创建一个可缓存的线程池。如果线程池的大小超过了处理任务所需要的线程，
那么就会回收部分空闲（60秒不执行任务）的线程，
当任务数增加时，此线程池又可以智能的添加新线程来处理任务。
此线程池不会对线程池大小做限制，线程池大小完全依赖于操作系统（或者说JVM）能够创建的最大线程大小
 * @author Administrator
 *
 */
public class CacheThreadExecutorTest {
    
    public static void main(String[] args) {
        MyThread t1 = new MyThread("AAA");
        MyThread t2 = new MyThread("BBB");
        MyThread t3 = new MyThread("CCC");
        MyThread t4 = new MyThread("DDD");
        
        ExecutorService singleThreadExecutor = Executors.newCachedThreadPool();
        
        singleThreadExecutor.execute(t1);
        singleThreadExecutor.execute(t2);
        singleThreadExecutor.execute(t3);
        singleThreadExecutor.execute(t4);
        
        singleThreadExecutor.shutdown();
    }
    

}
ScheduledThreadExecutor
package com.future.demo.threadPool;

import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/***
 * 创建一个大小无限的线程池。此线程池支持定时以及周期性执行任务的需求。
 * @author Administrator
 *
 */
public class ScheduledThreadExecutorTest {
    public static void main(String[] args) {
        ScheduledThreadPoolExecutor exec = new ScheduledThreadPoolExecutor(2);

        exec.scheduleAtFixedRate(new Runnable() {// 每隔一段时间就触发异常

            @Override
            public void run() {

                System.out.println("================");

            }

        }, 1, 1, TimeUnit.SECONDS);

        exec.scheduleAtFixedRate(new Runnable() {// 每隔一段时间打印系统时间，证明两者是互不影响的

            public void run() {

                System.out.println(System.nanoTime());

            }

        }, 1, 100, TimeUnit.MILLISECONDS);

    }
}

线程组

ThreadGroup
package com.future.demo.threadgroup;

public class ThreadGroupTest {
    public static void main(String[] args) throws Exception {
        ThreadGroup group = new ThreadGroup("main Thread");
        Thread t1 = new Thread(group,"AAA") {
            @Override
            public void run() {
                while(true) {
                    System.out.println(Thread.currentThread().getName()+"执行");
                }
            }
        };
        Thread t2 = new Thread(group,"BBB") {
            @Override
            public void run() {
                while(true) {
                    System.out.println(Thread.currentThread().getName()+"执行");
                }
            }
        };
        
        t1.start();
        t2.start();
        
        Thread.sleep(5000);
        
        System.out.println(Thread.currentThread().getThreadGroup().activeCount());
        
        group.list();
    }
}
package com.future.demo.conn;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReentrantLock;

public class NormalConnectionPool {
    private Map<String, Connection> connPool = new HashMap<String, Connection>();
    private ReentrantLock lock = new ReentrantLock();

    public Connection getConnection(String key) {

        Connection conn = null;

        try {
            lock.lock();

            if (connPool.containsKey(key)) {
                conn = connPool.get(key);
            } else {
                // 创建连接对象
                conn = crateConn();
                connPool.put(key, conn);
            }

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

        return conn;
    }

    private Connection crateConn() {
        return new Connection();
    }

    public static void main(String[] args) throws Exception {
        NormalConnectionPool pool = new NormalConnectionPool();
        long start = System.currentTimeMillis();
        
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 0; i < 200000; i++) {
                    Connection conn = pool.getConnection("KK");
                    System.out.println("KK-----"+conn);
                }
            }
        });
        
        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 0; i < 200000; i++) {
                    Connection conn = pool.getConnection("YY");
                    System.out.println("YY-----"+conn);
                }
            }
        });
        
        Thread t3 = new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 0; i < 200000; i++) {
                    Connection conn = pool.getConnection("FF");
                    System.out.println("FF-----"+conn);
                }
            }
        });
        
        t1.start();t2.start();t3.start();
        t1.join();t2.join();t3.join();
        
        long end = System.currentTimeMillis();
        System.out.println(end - start);
    }
}

class Connection {

}
package com.future.demo.conn;

import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

public class SuperConnectionPool {
    
    private ConcurrentHashMap<String, FutureTask<Connection>> connPool = new ConcurrentHashMap<>();

    public Connection getConnection(String key) {
        Connection conn = null;
        FutureTask<Connection> connectionTask = connPool.get(key);
        
        if (connectionTask != null) {
            try {
                conn = connectionTask.get();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
        } else {
            Callable<Connection> callable = new Callable<Connection>() {

                @Override
                public Connection call() throws Exception {
                    return new Connection();
                }
                
            };
            FutureTask<Connection> newTask = new FutureTask<>(callable);
            connPool.putIfAbsent(key, newTask);
            if (connectionTask == null) {
                connectionTask = newTask;
                connectionTask.run();
            }
        }
        
        try {
            conn = connectionTask.get();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
        
        return conn;
    }

    public static void main(String[] args) throws InterruptedException {
        SuperConnectionPool pool = new SuperConnectionPool();
        long start = System.currentTimeMillis();
        
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 0; i < 200000; i++) {
                    Connection conn = pool.getConnection("KK");
                    System.out.println("KK-----"+conn);
                }
            }
        });
        
        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 0; i < 200000; i++) {
                    Connection conn = pool.getConnection("YY");
                    System.out.println("YY-----"+conn);
                }
            }
        });
        
        Thread t3 = new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 0; i < 200000; i++) {
                    Connection conn = pool.getConnection("FF");
                    System.out.println("FF-----"+conn);
                }
            }
        });
        
        t1.start();t2.start();t3.start();
        t1.join();t2.join();t3.join();
        
        long end = System.currentTimeMillis();
        System.out.println(end - start);
    }
}
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原文地址：https://www.cnblogs.com/sunBinary/p/10597053.html