如何在关闭应用程序后使变量存储值？

Question

well i have this class Launcher.java :

public class Launcher {

public static void main(String... args){

    new App();
    System.out.println( "Innovate's current build is : " + App.getBuild());
}


}

and the class App.java :

import javax.swing.*;

public class App extends JFrame {

static int build;

public App(){

    super("Innovate");
    setBuild(getBuild() + 1);
    setVisible(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(500,200);
    setResizable(false);

}

public static void setBuild(int inc){
    build = inc;
}

public static int getBuild(){
    return build;
}

}

I am trying to make it every time the application is run the build number increments by 1, however whenever i run it prints out 1 and does not increment, how will i go about doing this?

thanks

Answer 1

You could go ahead and serialize the build number. because it will be lost every time the application is shut down.

Here is a tutorial on how to serialize objects

Answer 2

static int build;

You have to save the build number into file when your are exiting from your app. While creating your first App class object you have read from file and save it into your build variable. you can use Static Initializer Block for reading data from file because static block is executed only once: the first time you make an object of that class or the first time you access a static member of that class (even if you never make an object of that class).

Answer 3

As others have mentioned, you can use serialization to persist the state of the object, or you could read / write the value to something like a properties file. While these will work I'm not sure its the best solution for what you are trying to to. If you are trying to keep track of a build number for your application, typically that would be kept as a static value from within your project and only change every time you truly deploy your app, whether it be a release/snapshot/etc. Hope that helps.