Overriding finalize() method instance code in Java

The main research in this article is an attempt to override the finalize() method in Java, and the specific implementation is as follows.

Test code

 package com.alio.gc;/** * Execution result: * */public class FinalizeEscapeGC{ public static FinalizeEscapeGC instance=null; public void isAlive(){ System.out.println("yes,i am still alive"); } @Override protected void finalize() throws Throwable { super.finalize(); System.out.println("finalize method executed"); instance=this; } public static void main(String [] args) throws InterruptedException { instance=new FinalizeEscapeGC(); instance=null; System.gc(); Thread.sleep(1000); instance.isAlive(); //When the finalize method is not rewrite, the instance=nullpointerException will definitely be reported; System.gc(); Thread.sleep(1000); instance.isAlive(); }}

Execution results:

finalize method executed
yes,i am still alive
Exception in thread "main" java.lang.NullPointerException
at com.alio.gc.FinalizeEscapeGC.main(FinalizeEscapeGC.java:29)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)

Explanation:

First execute instance=null; then execute instance.isAlive(); when the finalize method is not rewrite, a nullpointerException will definitely be reported.
However, the actual execution result is a success in escape and a failure. This is because the finalize() method of any object will only be automatically called once by the system. If the object faces the next recycle, its finalize() method will not be executed again

Summarize

This way of saving the object is extremely uncertain. It is recommended that you do not need to use it and forget the existence of this method.

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