java 清理缓存

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

public class SimpleCache {
    private final Map<String, CacheEntry> cache = new HashMap<>();

    public Object get(String key) {
        CacheEntry entry = cache.get(key);
        if (entry != null && !entry.isExpired()) {
            return entry.value;
        }
        return null;
    }

    public void put(String key, Object value, long ttlMillis) {
        cache.put(key, new CacheEntry(value, ttlMillis));
    }

    private static class CacheEntry {
        private final Object value;
        private final long expirationTime;

        public CacheEntry(Object value, long ttlMillis) {
            this.value = value;
            this.expirationTime = System.currentTimeMillis() + ttlMillis;
        }

        public boolean isExpired() {
            return System.currentTimeMillis() > expirationTime;
        }
    }

    public static void main(String[] args) {
        SimpleCache cache = new SimpleCache();
        cache.put("key1", "value1", 5000); // 缓存5秒
        System.out.println(cache.get("key1")); // 应该输出"value1"
        try {
            Thread.sleep(6000); // 等待6秒
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(cache.get("key1")); // 应该输出null，因为已经过期
    }
}