读写锁

水深无声 2021-09-30 03:56 404阅读 0赞

import java.util.HashMap;
    import java.util.Map;
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    import java.util.concurrent.locks.ReentrantReadWriteLock;
    
    // 读写锁
    public class T8 {
    
        public static void main(String[] args) {
            MyCache myCache = new MyCache();
            for (int i = 1; i <= 5; i++) {
                final int temp = i;
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        myCache.put(temp+"",temp+"");
                    }
                },String.valueOf(temp)).start();
            }
    
            for (int i = 1; i <= 5; i++) {
                final int temp = i;
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        myCache.read(temp+"");
                    }
                },String.valueOf(temp)).start();
            }
        }
    }
    
    
    class MyCache{
        private volatile Map<String,Object> map = new HashMap<>();
    
        private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();  // 可重入的读写锁
    
        public void put(String key,Object value){
            lock.writeLock().lock();
            try {
                System.out.println(Thread.currentThread().getName()+"   正在写入..."+key);
                try {
                    Thread.sleep(3000);
                } catch (Exception e){
                    e.printStackTrace();
                }
                map.put(key,value);
                System.out.println(Thread.currentThread().getName()+"   写入完成...");
            } catch (Exception e){
                e.printStackTrace();
            } finally {
             lock.writeLock().unlock();
            }
    
        }
    
        public Object read(String key){
    
            lock.readLock().lock();
    
            try {
                System.out.println(Thread.currentThread().getName()+"   正在读取...");
                try {
                    Thread.sleep(1000);
                } catch (Exception e){
                    e.printStackTrace();
                }
                Object result = map.get(key);
                System.out.println(Thread.currentThread().getName()+"   读取完成..."+result);
    
                return result;
            } catch (Exception e){
                e.printStackTrace();
            } finally {
    
                lock.readLock().unlock();
                return null;
            }
        }
    }

结果：

D:\Application\Java\jdk1.8.0_201\bin\java.exe "-javaagent:D:\Application\IntelliJ IDEA 2018.3.4\lib\idea_rt.jar=63784:D:\Application\IntelliJ IDEA 2018.3.4\bin" -Dfile.encoding=UTF-8 -classpath D:\Application\Java\jdk1.8.0_201\jre\lib\charsets.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\deploy.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\access-bridge-64.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\cldrdata.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\dnsns.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\jaccess.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\jfxrt.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\localedata.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\nashorn.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\sunec.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\sunjce_provider.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\sunmscapi.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\sunpkcs11.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\ext\zipfs.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\javaws.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\jce.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\jfr.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\jfxswt.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\jsse.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\management-agent.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\plugin.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\resources.jar;D:\Application\Java\jdk1.8.0_201\jre\lib\rt.jar;D:\Workspace\flutter\letsJava\target\classes T8
    1   正在写入...1
    1   写入完成...
    2   正在写入...2
    2   写入完成...
    3   正在写入...3
    3   写入完成...
    4   正在写入...4
    4   写入完成...
    5   正在写入...5
    5   写入完成...
    2   正在读取...
    1   正在读取...
    3   正在读取...
    4   正在读取...
    5   正在读取...
    2   读取完成...2
    1   读取完成...1
    4   读取完成...4
    5   读取完成...5
    3   读取完成...3
    
    Process finished with exit code 0