java/w8/Cache.java

import java.util.HashMap;
import java.util.Map;

public class Cache<K, V> {
    private Map<K, CacheEntry> cacheMap;

    public Cache() {
        cacheMap = new HashMap<>();
    }

    public void put(K key, V value) {
        cacheMap.put(key, new CacheEntry(value));
    }

    public void put(K key, V value, long expireTimeMs) {
        cacheMap.put(key, new CacheEntry(value, expireTimeMs));
    }

    public V get(K key) {
        CacheEntry entry = cacheMap.get(key);
        if (entry == null) {
            return null;
        }
        if (entry.isExpired()) {
            cacheMap.remove(key);
            return null;
        }
        entry.updateAccessTime();
        return entry.getValue();
    }

    public boolean containsKey(K key) {
        CacheEntry entry = cacheMap.get(key);
        if (entry == null) {
            return false;
        }
        if (entry.isExpired()) {
            cacheMap.remove(key);
            return false;
        }
        return true;
    }

    public V remove(K key) {
        CacheEntry entry = cacheMap.remove(key);
        return entry != null ? entry.getValue() : null;
    }

    public int size() {
        return cacheMap.size();
    }

    public void clear() {
        cacheMap.clear();
    }

    private class CacheEntry {
        private V value;
        private long createTime;
        private long accessTime;
        private long expireTimeMs;

        public CacheEntry(V value) {
            this(value, -1);
        }

        public CacheEntry(V value, long expireTimeMs) {
            this.value = value;
            this.expireTimeMs = expireTimeMs;
            this.createTime = System.currentTimeMillis();
            this.accessTime = this.createTime;
        }

        public V getValue() {
            return value;
        }

        public void updateAccessTime() {
            this.accessTime = System.currentTimeMillis();
        }

        public boolean isExpired() {
            if (expireTimeMs <= 0) {
                return false;
            }
            return System.currentTimeMillis() > createTime + expireTimeMs;
        }

        public long getCreateTime() {
            return createTime;
        }

        public long getAccessTime() {
            return accessTime;
        }
    }
}