How to make a Java program that cannot be killed from command line? [duplicate]

问题

I am trying to run a Java program that appears to have "9 lives". It simply prints out, in an infinite loop, the following when we run it:

GlobalVar = 1
GlobalVar = 1
GlobalVar = 1
/* etc */
GlobalVar = 1
GlobalVar = 1

Then once we CTRL+C and kill the program, rather than quitting and going to the command prompt ... it should continue anew like this:

GlobalVar = 2
GlobalVar = 2
GlobalVar = 2

And on and on, it should re-open with the GlobalVar set to 3, 4, 5 etc.

Firstly, I know that This code is slightly impractical - it is just for academic exercise. But I am learning the Java.

Here my code so far :

import java.io.*;
public class SHTest {  

            static int globalVar = 0;

 public static void main ( String[] args ) throws  IOException  , InterruptedException {

        System.out.println ("The Global Var is " + globalVar);
        Runtime.getRuntime ().addShutdownHook ( new Thread () {
            @Override
            public void run () {

            globalVar += 1;
 /* shutdown */
           String[] command = {"C://Program Files//Java//jdk1.7.0_02//bin//java.exe", "SHTest"};  //args[0] ... CreateTexts
           ProcessBuilder pb = new ProcessBuilder(command);
           pb.redirectErrorStream(true);

           try {
               Process exec = pb.start(); 
               BufferedReader br = new BufferedReader(new InputStreamReader(exec.getInputStream()));
               String text = null;
           while ((text = br.readLine()) != null) {
               System.out.println(text);
           }

           System.out.println("Process exited with " + exec.waitFor());
           } 

            catch(IOException io) { }

            catch(InterruptedException inter) { }


            }
        } );  //end addShutdownHook() 

        //int copyGlobalVar = globalVar;
        while ( true  ) {
            System.out.println ( "Looping " + globalVar );
            Thread.sleep ( 800 );
        }
    }


    }

Reference:

Capture SIGINT in Java

Why can't I re-execute a Java program from within an Exception block?

addShutdownHook method

NOTE: I am open to using windows batch files as the JVM seems to have its own limitations with these things. Or other tools too. Even for Linux OS , would be Ok

回答1:

The static variable globalVar will not survive the destruction and recreation of the process. In the new process, it will be reinitialized to 0. It should be passed as a parameter to the process, and globalVar should then be initialized to the value of that argument.

回答2:

Runtime.getRuntime ().addShutdownHook is called before the JVM stops the program, but it does not prevent from stopping it.

If you want to intercept SIGINT signals, you'll need to use a SignalHandler (sun.misc.SignalHandler) on Unix as well as on Windows. See this article (pdf, page 8 and 9).

Here is a simple example on how to use it :

Signal.handle(new Signal("INT"), new SignalHandler () {
  public void handle(Signal sig) {
    if (globalVar == 9) {
      System.out.println("9 lifes consumes, program will shutdown");
      System.exit();
    }
    System.out.println(globalVar + " lifes consumed, one more will be consumed");
    // increment your score here
  }
});

Source : this post.

来源：https://stackoverflow.com/questions/31506485/how-to-make-a-java-program-that-cannot-be-killed-from-command-line

标签

java

shutdown-hook