Java WeakHashMap的深度解析：如何利用弱引用实现弱缓存策略？

Object obj = new Object();
WeakReference<Object> weakObj = new WeakReference<Object>(obj);

public class WeakCache<K, V> {
    private final Map<K, WeakReference<V>> cache = new WeakHashMap<K, WeakReference<V>>();

    public V get(K key) {
        WeakReference<V> ref = cache.get(key);
        V value = null;
        if (ref != null) {
            value = ref.get();
        }
        if (value == null) {
            value = create(key);
            cache.put(key, new WeakReference<V>(value));
        }
        return value;
    }

    private V create(K key) {
        // 从数据库或网络中查询数据，并返回结果
    }
}

package com.example.java.demo.javaTest.map;

import com.sun.beans.WeakCache;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.concurrent.TimeUnit;

/**
 * @Date 2023-09-09 22:30
 */
@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class WeakCacheTest {

    private WeakCache<Integer, String> cache;

    @Before
    public void setUp() {
        cache = new WeakCache<Integer, String>();
    }

    @Test
    public void testCache() throws Exception {
        //先缓存一个key
        cache.put(1,"v");

        String value = cache.get(1);
        System.out.println("value = " + value);
        Assert.assertNotNull(value);
        //等待10s
        TimeUnit.SECONDS.sleep(10);
        //垃圾回收
        System.gc();
        value = cache.get(1);
        System.out.println("value = " + value);
        Assert.assertNotNull(value);
    }
}