private final Map attributes = new HashMap();//整个方法上锁public synchronized boolean userLocationMatches(String name, String regexp) {
        String key = "users." + name + ".location";
        String location = attributes.get(key);if (location == null)return false;elsereturn Pattern.matches(regexp, location);
    }public boolean userLocationMatches(String name, String regexp) {
        String key = "users." + name + ".location";
        String location;//只针对可变状态上锁synchronized (this) {
            location = attributes.get(key);
        }if (location == null)return false;elsereturn Pattern.matches(regexp, location);
    }

public class ServerStatusBeforeSplit {public final Set users;public final Set queries;public ServerStatusBeforeSplit() {
        users = new HashSet();
        queries = new HashSet();
    }//每个方法使用 当前class实例锁，类似于synchronized(this),不管是否是操作同一共享状态public synchronized void addUser(String u) {
        users.add(u);
    }public synchronized void addQuery(String q) {
        queries.add(q);
    }public synchronized void removeUser(String u) {
        users.remove(u);
    }public synchronized void removeQuery(String q) {
        queries.remove(q);
    }
}public class ServerStatusAfterSplit {public final Set users;public final Set queries;//操作同一 状态的方法 使用相同的锁public ServerStatusAfterSplit() {
        users = new HashSet();
        queries = new HashSet();
    }public void addUser(String u) {synchronized (users) {
            users.add(u);
        }
    }public void addQuery(String q) {synchronized (queries) {
            queries.add(q);
        }
    }public void removeUser(String u) {synchronized (users) {
            users.remove(u);
        }
    }public void removeQuery(String q) {synchronized (users) {
            queries.remove(q);
        }
    }
}

//Map分段锁实现public class StripedMap {// Synchronization policy: buckets[n] guarded by locks[n%N_LOCKS]private static final int N_LOCKS = 16;  //锁数量private final Node[] buckets;           //容器桶private final Object[] locks;           //同步监听器对象数组private static class Node {
        Node next;
        Object key;
        Object value;
    }public StripedMap(int numBuckets) {
        buckets = new Node[numBuckets];
        locks = new Object[N_LOCKS];for (int i = 0; i < N_LOCKS; i++)
            locks[i] = new Object();
    }private final int hash(Object key) {return Math.abs(key.hashCode() % buckets.length);
    }public Object get(Object key) {int hash = hash(key);//获取当前 key对应的index区域的锁，只获取了一个锁synchronized (locks[hash % N_LOCKS]) {for (Node m = buckets[hash]; m != null; m = m.next)if (m.key.equals(key))return m.value;
        }return null;
    }public void clear() {for (int i = 0; i < buckets.length; i++) {//获取 每个i对应的锁，就是获取了整个容器所有的分段锁synchronized (locks[i % N_LOCKS]) {
                buckets[i] = null;
            }
        }
    }
}