Java：看不到我的变量

Question

I have this small little code but I don't know why it cannot read the value of the aa.width from aa class in ab class.

I am trying to create a basic game. The file ab.java has the print statement. I know I am not calling the function in aa , but that's how java works. I thought I could just do aa.width and I will get the value as it is a public variable...thanks for your help

aa.java :

package com.Game;

import javax.swing.JFrame;

public class aa {

    public static ab f= new ab();
    public static int width = 600;
    public static int height = 400;
    public static void main(String args[]){

        f.setSize(width,height);
        f.setResizable(false);
        f.setVisible(true);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setTitle("game first");
        f.setLocationRelativeTo(null);
        System.out.println("main window running!");

    }
}

ab.java

package com.Game;

import java.awt.GridLayout;

import javax.swing.*;

public class ab extends JFrame {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    public ac panel;

    public ab() {
        panel = new ac(this);
        setLayout(new GridLayout (1,1,0,0));
        add(panel);
        System.out.format("the value of width %d\n", aa.width);
    }

}

it prints out :

the value of width 0
main window running!

Answer 1

You are setting aa.width variable after calling ab() constructor. Move the public static int width = 600; one line up and you are done.

Answer 2

I would like to suggest you also not to use too much public variables, instead each object should have its private variables and a setter/getter method. I suggest you also to check the structure of your game and the way you are trying to create it, if you are very new to java GUI and/or MVC (model view controller) maybe you want only to create a single class with what you need all inside or, one step further, a class handling the logic and a class handling all the graphics. If you do a great thinking before coding you probably will have a faster coding and debugging.

I cannot tell you more because I cannot understand what your code wants to do.