JUC下的几种线程计数器以及读写锁
1-CountDownLanch--JUC
package thread20200414;import java.util.concurrent.CountDownLatch;/** CountDownLaunch做线程减法，即所有线程执行完后，才可以进行下一步 一个线程等待其他线程执行完毕后，才执行 * @author zhaomin * @date 2020/4/15 8:35 */public class CountDownLanchTest { public static void main(String[] args) { CountDownLatch countDownLatch=new CountDownLatch(6); for(int i=0;i<6;i++){ new Thread(()->{ System.out.println(Thread.currentThread().getName()+'--离开教室'); countDownLatch.countDown(); },String.valueOf(i)).start(); } try { countDownLatch.await(); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println('main离开教室'); }}
2- CyclicBarrier--JUC
package thread20200414;import java.util.concurrent.BrokenBarrierException;import java.util.concurrent.CyclicBarrier;/** * 线程加法，只有等到一定数量的线程都开启后，才进行下一步(执行runnable里的方法) * @author zhaomin * @date 2020/4/15 8:51 */public class CyclicBarrierTest { public static void main(String[] args) { Runnable runnable=new Runnable() { @Override public void run() { System.out.println('集齐7颗龙珠，召唤神龙'); } }; CyclicBarrier cyclicBarrier=new CyclicBarrier(7,runnable); for(int i=0;i<7;i++){ final int count=i;//Lambda表达式中的变量必须是final的 new Thread(()->{ System.out.println(count+'颗龙珠'); try { cyclicBarrier.await(); } catch (InterruptedException e) { e.printStackTrace(); } catch (BrokenBarrierException e) { e.printStackTrace(); } },String.valueOf(i)).start(); } }}
3-Semaphore--JUC
package thread20200414;import java.util.concurrent.Semaphore;import java.util.concurrent.TimeUnit;/** * 抢车位，狼多肉少-3个资源6和线程 * @author zhaomin * @date 2020/4/15 15:06 */public class SemaphoreTest { public static void main(String[] args) { Semaphore semaphore=new Semaphore(3); for(int i=1;i<=6;i++){ new Thread(()->{ try { semaphore.acquire();//获取到了资源，就让资源数减一 System.out.println(Thread.currentThread().getName()+'抢占车位'); TimeUnit.SECONDS.sleep(3); System.out.println(Thread.currentThread().getName()+'离开车位'); } catch (InterruptedException e) { e.printStackTrace(); }finally { semaphore.release();//释放资源就让资源加一 } },String.valueOf(i)).start(); } }}
4-读写锁
读读可共享--写读、写写要独占
package thread20200414;import com.sun.org.apache.xpath.internal.SourceTree;import java.util.HashMap;import java.util.Map;import java.util.concurrent.TimeUnit;import java.util.concurrent.locks.ReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;/** * 读写锁 * 读读可同时 * 读写、写写要独占 * @author zhaomin * @date 2020/4/15 16:10 */class Book{ private volatile Map<String,String> map=new HashMap<>(); ReadWriteLock readWriteLock=new ReentrantReadWriteLock(); public void put(String key, String val) { readWriteLock.writeLock().lock();//加写锁 try{ System.out.println('正在写---'); map.put(key,val); try { TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(Thread.currentThread().getName()+'写入-'+key); System.out.println('写完了---'); }finally { readWriteLock.writeLock().unlock(); } } public void get(String key){ readWriteLock.readLock().lock();//加读锁 try{ System.out.println('读书中---'); String s = map.get(key); try { TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(Thread.currentThread().getName()+'读取-'+s); System.out.println('读完了---'); }finally { readWriteLock.readLock().unlock(); } }}public class ReadWriteLockTest { public static void main(String[] args) { Book book=new Book(); for(int i=1;i<5;i++) { final int tem=i; new Thread(()->{ book.put(String.valueOf(tem),String.valueOf(tem)); },String.valueOf(i)).start(); } for (int i=1;i<=5;i++) { final int tem=i; new Thread(()->{ book.get(String.valueOf(tem)); },String.valueOf(i)).start(); } }}