重入锁
package com.thread.demo.safe.lock;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;/** * 重入锁 * * @author Administrator * */public class LockDemo1 { private static int count; private static Lock lock = new ReentrantLock(); public static void main(String[] args) throws Exception { Thread t1 = new Thread(new MyRunnable(), "AAA"); Thread t2 = new Thread(new MyRunnable(), "BBB"); t2.start(); Thread.sleep(2000); t1.start(); t1.join(); t2.join(); System.out.println("最终结果为:" + count); } static class MyRunnable implements Runnable { public void increase() { // 加锁 lock.lock(); try { count++; System.out.println(Thread.currentThread().getName() + "计算中...."); Thread.sleep(4000);// 模拟操作耗时 System.out.println(Thread.currentThread().getName() + "计算完成..."); // throw new RuntimeException(); } catch (NumberFormatException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } finally { // 解锁 lock.unlock(); } } public void increase1() { if (lock.tryLock()) { try { count++; //System.out.println(Thread.currentThread().getName() + "计算中...."); Thread.sleep(1000);// 模拟操作耗时 System.out.println(Thread.currentThread().getName() + "计算完成..."); } catch (NumberFormatException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } finally { // 解锁 lock.unlock(); } } else { System.out.println(Thread.currentThread().getName()); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } } } public void run() { for (int i = 0; i < 10; i++) { increase1(); } } }} 读写锁
package com.thread.demo.safe.lock;import java.util.Random;import java.util.concurrent.locks.ReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;class ReadWrite { /* 共享数据，只能一个线程写数据，可以多个线程读数据 */ private Object data = null; /* 创建一个读写锁 */ ReadWriteLock rwlock = new ReentrantReadWriteLock(); /** * 读数据，可以多个线程同时读， 所以上读锁即可 */ public void get() { /* 上读锁 */ rwlock.readLock().lock(); try { System.out.println(Thread.currentThread().getName() + " 准备读数据!"); /* 休眠 */ Thread.sleep((long) (Math.random() * 1000)); System.out.println(Thread.currentThread().getName() + "读出的数据为 :" + data); } catch (InterruptedException e) { e.printStackTrace(); } finally { rwlock.readLock().unlock(); } } /** * 写数据，多个线程不能同时 写 所以必须上写锁 * * @param data */ public void put(Object data) { /* 上写锁 */ rwlock.writeLock().lock(); try { System.out.println(Thread.currentThread().getName() + " 准备写数据!"); /* 休眠 */ Thread.sleep((long) (Math.random() * 1000)); this.data = data; System.out.println(Thread.currentThread().getName() + " 写入的数据: " + data); } catch (Exception e) { e.printStackTrace(); } finally { rwlock.writeLock().unlock(); } }} /** * 测试类 * */public class ReadWriteLockDemo { public static void main(String[] args) { /* 创建ReadWrite对象 */ final ReadWrite readWrite = new ReadWrite(); /* 创建并启动3个读线程 */ for (int i = 0; i < 3; i++) { new Thread(new Runnable() { @Override public void run() { readWrite.get(); } },"AAA"+i).start(); /*创建3个写线程*/ new Thread(new Runnable() { @Override public void run() { /*随机写入一个数*/ readWrite.put(new Random().nextInt(8)); } },"BBB"+i).start(); } } } 读写锁的实例(缓存)
package com.thread.demo.safe.lock;import java.util.Collections;import java.util.HashMap;import java.util.Map;import java.util.concurrent.locks.ReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;/** * 读写锁的实例 * * @author Administrator * */public class CacheDemo { // 创建一个缓存对象 static Map cache = Collections.synchronizedMap(new HashMap<>()); static ReadWriteLock rwLock = new ReentrantReadWriteLock(); /** * 定义一个获取数据的方法 */ public Object getData(String key) { // 开启读锁 rwLock.readLock().lock(); Object value = null; try { // 获取到缓冲对象中数据 value = cache.get(key); if (value == null) { // 关闭读锁 rwLock.readLock().unlock(); // 开启写锁 rwLock.writeLock().lock(); try { value = cache.get(key); // 再次判断是为空 if (value == null) { // 把数据存储到缓存中 System.out.println("从db获取数据"+key); cache.put(key, "key的值"); } } finally { // 释放写锁 rwLock.writeLock().unlock(); } // 打开读锁 rwLock.readLock().lock(); } System.out.println("从缓存获取"); value = cache.get(key); } finally { // 关闭读锁 rwLock.readLock().unlock(); } return value; } static class CacheRunnable implements Runnable { @Override public void run() { for (int i = 0; i < 3; i++) { System.out.println(Thread.currentThread().getName()); System.out.println(new CacheDemo().getData(i+"")); } } } public static void main(String[] args) { // 放入数据 //cache.put("1", "1111"); //cache.put("2", 22222); for ( int i = 0; i < 3; i++) { new Thread(new CacheRunnable(),"AAA"+i).start(); } }}