“对于任何给定对象，JVM 永远不会多次调用 finalize 方法”的含义。在物体复活的情况下？

Question

根据 Java 文档：

对于任何给定对象，Java 虚拟机永远不会多次调用 finalize 方法。

1. 上述政策可以帮助使对象不朽吗？如果我从 finalize() 方法中一次复活一个对象，那么该对象是否会成为不朽的，因为 JVM 不能第二次在该对象上调用 finalize() 方法？

或者

1. 如果该对象再次符合 GC 条件（假设指向复活对象的另一个引用符合 GC 条件），那么下次 JVM 将删除该对象而不调用该对象的 finalize() 方法？

我试图通过一些示例代码来验证它并假设第二个是正确的，但需要确认我的理解。

Answer 1

根据 ernest_k，它是第 2 个。该对象将被垃圾收集，而无需调用其 finalize() 方法。添加我的示例代码来完成这个答案，我创建它来验证。import java.util.HashSet;import java.util.Set;class Immortal {&nbsp; &nbsp; // making it public and non-fianl to modify from outside&nbsp; &nbsp; public static Set<Immortal> immortals = new HashSet<>();&nbsp; &nbsp; @Override&nbsp; &nbsp; protected void finalize() throws Throwable {&nbsp; &nbsp; &nbsp; &nbsp; System.out.println("Running finalize for " + this);&nbsp; &nbsp; &nbsp; &nbsp; immortals.add(this); // Resurrect the object by creating a new reference&nbsp; &nbsp; }}public class ObjectResurrection {&nbsp; &nbsp; public static void callGC() {&nbsp; &nbsp; &nbsp; &nbsp; // call garbage collection&nbsp; &nbsp; &nbsp; &nbsp; System.gc();&nbsp; &nbsp; &nbsp; &nbsp; // wait for some time to give chance to run garbage collection thread&nbsp; &nbsp; &nbsp; &nbsp; try {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Thread.sleep(10 * 1000);&nbsp; &nbsp; &nbsp; &nbsp; } catch (InterruptedException e) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // TODO Auto-generated catch block&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; e.printStackTrace();&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; public static void main(String[] args) {&nbsp; &nbsp; &nbsp; &nbsp; Immortal immortal1 = new Immortal();&nbsp; &nbsp; &nbsp; &nbsp; Immortal immortal2 = new Immortal();&nbsp; &nbsp; &nbsp; &nbsp; // print objects when they are alive.&nbsp; &nbsp; &nbsp; &nbsp; System.out.println("immortal1 = " + immortal1);&nbsp; &nbsp; &nbsp; &nbsp; System.out.println("immortal2 = " + immortal2);&nbsp; &nbsp; &nbsp; &nbsp; // print immortal set&nbsp; &nbsp; &nbsp; &nbsp; System.out.println("immortal set = " + Immortal.immortals);&nbsp; &nbsp; &nbsp; &nbsp; // make all objects garbage collectable&nbsp; &nbsp; &nbsp; &nbsp; immortal1 = null;&nbsp; &nbsp; &nbsp; &nbsp; immortal2 = null;&nbsp; &nbsp; &nbsp; &nbsp; callGC();&nbsp; &nbsp; &nbsp; &nbsp; // now objects will be null&nbsp; &nbsp; &nbsp; &nbsp; System.out.println("immortal1 = " + immortal1);&nbsp; &nbsp; &nbsp; &nbsp; System.out.println("immortal2 = " + immortal2);&nbsp; &nbsp; &nbsp; &nbsp; // but stays in immortal set&nbsp; &nbsp; &nbsp; &nbsp; System.out.println("immortal set = " + Immortal.immortals);&nbsp; &nbsp; &nbsp; &nbsp; // remove all objects from immortal set, and make them again eligible for GC&nbsp; &nbsp; &nbsp; &nbsp; Immortal.immortals.clear();&nbsp; &nbsp; &nbsp; &nbsp; callGC();&nbsp; &nbsp; &nbsp; &nbsp; // again print the immortal set&nbsp; &nbsp; &nbsp; &nbsp; // this time set will be empty, and those 2 objects will be destroyed by Garbage&nbsp; &nbsp; &nbsp; &nbsp; // Collection,&nbsp; &nbsp; &nbsp; &nbsp; // but this time they will not call finalize, because it is already called&nbsp; &nbsp; &nbsp; &nbsp; // you can notice no output from finalize method in the output this time&nbsp; &nbsp; &nbsp; &nbsp; System.out.println("immortal set = " + Immortal.immortals);&nbsp; &nbsp; }}上述程序的输出（在我的机器上）：immortal1 = effective.java.item7.finalizer6.Immortal@70dea4eimmortal2 = effective.java.item7.finalizer6.Immortal@5c647e05immortal set = []Running finalize for effective.java.item7.finalizer6.Immortal@5c647e05Running finalize for effective.java.item7.finalizer6.Immortal@70dea4eimmortal1 = nullimmortal2 = nullimmortal set = [effective.java.item7.finalizer6.Immortal@5c647e05, effective.java.item7.finalizer6.Immortal@70dea4e]immortal set = []