多线程四个辅助类的简单应用

灰太狼 2022-05-15 02:23 183阅读 0赞

# 一、CountDownLatch #

import java.io.BufferedReader;
    import java.io.FileReader;
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.concurrent.CountDownLatch;
    /** * CountDownLatch 用于文本文件中多行数字求和 * @author superman * */
    public class Demo2 { 
    
        private int[] nums;
    
        public Demo2(int line) {
            nums = new int[line];
        }
    
        public void calc(String line, int index, CountDownLatch latch) {
            String[] nus = line.split(","); // 切分出每个值
            int total = 0;
            for (String num : nus) {
                total += Integer.parseInt(num);
            }
            nums[index] = total; // 把计算的结果放到数组中指定的位置
            System.out.println(Thread.currentThread().getName() + " 执行计算任务... " + line + " 结果为：" + total);
            latch.countDown();
        }
    
        public void sum() {
            System.out.println("汇总线程开始执行... ");
            int total = 0;
            for (int i = 0; i < nums.length; i++) {
                total += nums[i];
            }
            System.out.println("最终的结果为：" + total);
        }
    
        public static void main(String[] args) {
    
            List<String> contents = readFile();
            int lineCount = contents.size();
    
            CountDownLatch latch = new CountDownLatch(lineCount);
    
            Demo2 d = new Demo2(lineCount);
            for (int i = 0; i < lineCount; i++) {
                final int j = i;
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        d.calc(contents.get(j), j, latch);
                    }
                }).start();
            }
    
            try {
                latch.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    
            d.sum();
        }
    
        private static List<String> readFile() {
            List<String> contents = new ArrayList<>();
            String line = null;
            BufferedReader br = null;
            try {
                br = new BufferedReader(new FileReader("nums.txt"));
                while ((line = br.readLine()) != null) {
                    contents.add(line);
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if (br != null) {
                    try {
                        br.close();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
            return contents;
        }
    
    }

![这里写图片描述][70]

# 二、CyclicBarrier #

import java.util.Random;
    import java.util.concurrent.CyclicBarrier;
    /** * 控制多个线程同一时刻访问 * @author superman * */
    public class Demo { 
    
        Random random = new Random();
    
        public void meeting(CyclicBarrier barrier) {
            try {
                Thread.sleep(random.nextInt(4000));
            } catch (InterruptedException e1) {
                e1.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + " 到达会议室，等待开会..");
    
            if(Thread.currentThread().getName().equals("Thread-7")) {
                // Thread.currentThread().interrupt();
                try {
                    Thread.sleep(10000);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                barrier.reset();
    
            }
    
            try {
                barrier.await();
            } catch (Exception e) {
                e.printStackTrace();
            }
    
        }
    
        public static void main(String[] args) {
            Demo demo = new Demo();
    
            CyclicBarrier barrier = new CyclicBarrier(10, new Runnable() {
                @Override
                public void run() {
                    System.out.println("好！我们开始开会...");
                }
            });
    
            for (int i = 0; i < 10; i++) {
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        demo.meeting(barrier);
                    }
                }).start();
            }
    
            // 监控等待线程数
            new Thread(new Runnable() {
    
                @Override
                public void run() {
                    while(true) {
                        try {
                            Thread.sleep(1000);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        System.out.println("等待的线程数 " + barrier.getNumberWaiting());
                        System.out.println("is broken " + barrier.isBroken());
                    }
                }
            }).start();
        }
    
    }

# 三、Semaphore #

import java.util.concurrent.Semaphore;
    /** * 同一时间段访问资源的数量 * @author superman * */
    public class Demo { 
    
        public void method (Semaphore semaphore) {
    
            try {
                semaphore.acquire();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    
            System.out.println(Thread.currentThread().getName() + " is run ...");
    
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    
            semaphore.release();
        }
    
    
        public static void main(String[] args) {
    
            Demo d = new Demo();
            Semaphore semaphore = new Semaphore(10);
    
            while(true) {
    
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        d.method(semaphore);
                        try {
                            Thread.sleep(100);
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                    }
                }).start();
            }
    
    
        }
    
    }

# 四、Exchanger #

import java.util.concurrent.Exchanger;
    /** * 用于线程间信息的交换 * @author superman * */
    public class Demo { 
    
        public void a (Exchanger<String> exch) {
    
            System.out.println("a 方法执行...");
    
            try {
                System.out.println("a 线程正在抓取数据...");
                Thread.sleep(2000);
                System.out.println("a 线程抓取到数据...");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    
            String res = "12345";
    
            try {
                System.out.println("a 等待对比结果...");
                exch.exchange(res);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    
        }
    
        public void b (Exchanger<String> exch) {
            System.out.println("b 方法开始执行...");
            try {
                System.out.println("b 方法开始抓取数据...");
                Thread.sleep(4000);
                System.out.println("b 方法抓取数据结束...");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            String res = "12345";
    
            try {
                String value = exch.exchange(res);
                System.out.println("开始进行比对...");
                System.out.println("比对结果为：" + value.equals(res));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    
        public static void main(String[] args) {
    
            Demo d = new Demo();
            Exchanger<String> exch = new Exchanger<>();
            new Thread(new Runnable() {
                @Override
                public void run() {
                    d.a(exch);
                }
            }).start();
    
            new Thread(new Runnable() {
                @Override
                public void run() {
                    d.b(exch);
                }
            }).start();
    
        }
    
    }

[70]: /images/20220515/fdedcc8e23504d858afbbc9474bea3b8.png