【读写锁 ReadWriteLock 结合 LinkedHashMap】

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

public class ReadWriteHashMap<K, V> {

    private final Map<K, V> map;
    private final ReadWriteLock lock;
    private final ReadWriteLock.ReadLock rlock;
    private final ReadWriteLock.WriteLock wlock;

    public ReadWriteHashMap() {
        map = new LinkedHashMap<>();
        lock = new ReentrantReadWriteLock();
        rlock = lock.readLock();
        wlock = lock.writeLock();
    }

    public void put(K key, V value) {
        wlock().lock();
        try {
            map.put(key, value);
        } finally {
            wlock().unlock();
        }
    }

    public V get(K key) {
        rlock().lock();
        try {
            return map.get(key);
        } finally {
            rlock().unlock();
        }
    }

    public boolean containsKey(K key) {
        rlock().lock();
        try {
            return map.containsKey(key);
        } finally {
            rlock.unlock();
        }
    }
}