JUC powerful auxiliary class

JUC Powerful auxiliary classes

1. Reduce the count CountDownLatch

2. Recycling fence CyclicBarrier

3. Signal lamp Semaphore

Reduce the count CountDownLatch demonstration

package juc;

import java.util.concurrent.CountDownLatch;

// demonstration CountDownLatch

public class CountDownLatchDemo {

    //6 After the students left the classroom one after another , The monitor locked the door

    public static void main(String[] args) throws InterruptedException {

        // establish CountDownLatch object , Set initial value

        CountDownLatch countDownLatch = new CountDownLatch(6);

        //6 After the students left the classroom one after another

        for (int i=1; i <=6; i++) {

            new Thread(()->{

                System.out.println(Thread.currentThread().getName()+" Classmate No. left the classroom ");

                // Count -1

                countDownLatch.countDown();

            },String.valueOf(i)).start();

        }

        // wait for （ Turn into 0 Wait for the end ）

        countDownLatch.await();

        System.out.println(Thread.currentThread().getName()+" The monitor locked the door and left ");

    }

}

Recycling fence CyclicBarrier demonstration

package juc;

import java.util.concurrent.CyclicBarrier;

// Gather together 7 A dragon ball can summon a dragon

public class CyclicBarrierDemo {

    // Create a fixed value

    private static final int NUMBER = 7;

    public static void main(String[] args) {

        // establish CyclicBarrier

        CyclicBarrier cyclicBarrier = new CyclicBarrier(NUMBER, ()->{

            System.out.println(" Gather together 7 A dragon ball can summon a dragon ");

        });

        // Gather together 7 Dragon Ball process

        for (int i=1; i <=7; i++) {

            new Thread(()->{

                try {

                    System.out.println(Thread.currentThread().getName()+" The dragon balls were collected ");

                    // wait for

                    cyclicBarrier.await();

                } catch (Exception e) {

                    e.printStackTrace();

                }

            },String.valueOf(i)).start();

        }

    }

}

Signal lamp Semaphore demonstration

package juc;

import java.util.Random;

import java.util.concurrent.Semaphore;

import java.util.concurrent.TimeUnit;

//6 car , stop 3 A parking space

public class SemaphoreDemo {

    public static void main(String[] args) {

        // establish Semaphore, Set the number of licenses

        Semaphore Semaphore = new Semaphore(3);

        // simulation 6 car

        for (int i=1; i <=6; i++) {

            new Thread(()->{

                try {

                    // preemption

                    Semaphore.acquire();

                    System.out.println(Thread.currentThread().getName()+" Got the parking space ");

                    // Set random parking time

                    TimeUnit.SECONDS.sleep(new Random().nextInt(5));

                    System.out.println(Thread.currentThread().getName()+" Leaving the parking space ");

                } catch (InterruptedException e) {

                    e.printStackTrace();

                } finally {

                    // Release

                    Semaphore.release();

                }

            },String.valueOf(i)).start();

        }

    }

}