Java常用并发容器总结(一)

 //SynchronizedMap是Collections的一个内部类，表示同步的Map
 private static class SynchronizedMap<K,V>
        implements Map<K,V>, Serializable {
        private static final long serialVersionUID = 1978198479659022715L;

        private final Map<K,V> m;     
        final Object      mutex;        

        //使用一个线程不安全的Map构造SynchronizedMap,采用了包装设计模式
        SynchronizedMap(Map<K,V> m) {
            if (m==null)
                throw new NullPointerException();

            //这里对原Map进行了包装，原Map负责进行实际的操作，mutex锁对象进行加锁
            this.m = m;
            mutex = this;
        }

        SynchronizedMap(Map<K,V> m, Object mutex) {
            this.m = m;
            this.mutex = mutex;
        }

public V get(Object key) {
            synchronized (mutex) {return m.get(key);}
        }