我有下面的代码。我的期望是代码应该打印出来 Garbage Claimed 但它一直在打印实际对象的值 Test Object . 我已经允许 testWeakReference() 要弹出的框架 refTest 有资格进行垃圾收集。然后在测试 WeakReference 已经有人认领了。

import java.lang.ref.WeakReference;
import java.util.Optional;

public class WeakHashMapTest {
    public static void main(String[] args) throws InterruptedException {
        WeakReference<RefTest> weakReference = testWeakReference();
        Thread.sleep(10000l);
        System.out.println(Optional.ofNullable(weakReference.get()).map(RefTest::getValue).orElse("Garbage claimed"));
    }

    private static WeakReference<RefTest> testWeakReference() throws InterruptedException {
        RefTest refTest = new RefTest("Test Object");
        WeakReference<RefTest> weakReference = new WeakReference(refTest);
        return weakReference;
    }

    public static class RefTest {
        private String value;

        public RefTest(String val){
            this.value = val;
        }

        public String getValue(){
            return this.value;
        }
    }
}