Question

使用WeakReference和将强引用类型设置为null有什么区别？

例如，在下面的代码中，变量“test”是对“testString”的强引用。当我将“test”设置为null时。不再有强参考，因此“testString”现在符合GC的条件。因此，如果我可以简单地将对象引用“test”设置为null，那么具有WeakReference类型的重点是什么？

class CacheTest {
  private String test = "testString";

  public void evictCache(){
    test = null; // there is no longer a Strong reference to "testString" 
    System.gc(); //suggestion to JVM to trigger GC 
  }
}

为什么我要使用WeakReference？

class CacheTest {
  private String test = "testString";
  private WeakReference<String> cache = new WeakReference<String>(test);

  public void evictCache(){
    test = null; // there is no longer a Strong reference to "testString" 
    System.gc(); //suggestion to JVM to trigger GC 
  }
}

Answer 1

在您的示例中，两种情况之间没有区别。但是，请考虑以下与您的类似的示例：

class CacheTest {
  private String test = "testString";
  private String another = "testString";

  public void evictCache(){
    test = null; // this still doesn't remove "testString" from the string pool because there is another strong reference (another) to it.
    System.gc(); //suggestion to JVM to trigger GC 
  }
}

和

class CacheTest { private String test = "testString"; private WeakReference<String> cache = new WeakReference<String>(test); public void evictCache(){ test = null; // this removes "testString" from the pool because there is no strong reference; there is a weak reference only. System.gc(); //suggestion to JVM to trigger GC } }

弱引用vs设置为Null

1 个答案: