Java 定时删除map中的元素

需求
        在项目开发过程中，遇到需要在高并发情况下往map中插入数据，等数据被利用完成后，留在map中没有什么用处了，就需要定时将map中的元素删除。

核心代码

import java.util.Map;
import java.util.Date;
import java.text.SimpleDateFormat;
import java.util.concurrent.ConcurrentHashMap;

public class WeakConcurrentHashMap<K, V> extends ConcurrentHashMap<K, V> {

    private static final long serialVersionUID = 1L;

    private Map<K, Long> timeMap = new ConcurrentHashMap<K, Long>();
    private long expiryInMillis = 1000;
    private static final SimpleDateFormat sdf = new SimpleDateFormat("hh:mm:ss:SSS");

    public WeakConcurrentHashMap() {
        initialize();
    }

    public WeakConcurrentHashMap(long expiryInMillis) {
        this.expiryInMillis = expiryInMillis;
        initialize();
    }

    void initialize() {
        new CleanerThread().start();
    }

    @Override
    public V put(K key, V value) {
        Date date = new Date();
        timeMap.put(key, date.getTime());
        System.out.println("Inserting : " + sdf.format(date) + " : " + key + " : " + value);
        V returnVal = super.put(key, value);
        return returnVal;
    }

    @Override
    public void putAll(Map<? extends K, ? extends V> m) {
        for (K key : m.keySet()) {
            put(key, m.get(key));
        }
    }

    @Override
    public V putIfAbsent(K key, V value) {
        if (!containsKey(key))
            return put(key, value);
        else
            return get(key);
    }

    class CleanerThread extends Thread {
        @Override
        public void run() {
            System.out.println("Initiating Cleaner Thread..");
            while (true) {
                cleanMap();
                try {
                    Thread.sleep(expiryInMillis / 2);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }

        private void cleanMap() {
            long currentTime = new Date().getTime();
            for (K key : timeMap.keySet()) {
                if (currentTime > (timeMap.get(key) + expiryInMillis)) {
                    V value = remove(key);
                    timeMap.remove(key);
                    System.out.println("Removing : " + sdf.format(new Date()) + " : " + key + " : " + value);
                }
            }
        }
    }
}

测试结果

WeakConcurrentHashMap<String, Object> weakConcurrentHashMap = new WeakConcurrentHashMap<>(5000);
weakConcurrentHashMap.put("testKey", "testValue");
System.out.println(weakConcurrentHashMap);

System.out.println("线程睡眠了6秒");
Thread.sleep(6000);

System.out.println(weakConcurrentHashMap);

参考博客
https://stackoverflow.com/questions/3802370/java-time-based-map-cache-with-expiring-keys