无法从 actionlistener 内部增加变量

Question

I'm new to Java and just learning I want to increase a variable by clicking a button but I'm getting the following error

local variables referenced from an inner class must be final or effectively final
 
The assigned value is never used

Adding final doesn't solved the problem and I'm a bit stuck why this doesn't work? can you help?

public class JavaApplication2 {
    public static void main(String[] args) {
        // TODO code application logic here
        JFrame frame = new JFrame();
        JPanel panel = new JPanel();
        JButton button = new JButton("Click");
 
        panel.setLayout(new FlowLayout());
 
        frame.add(panel);
        panel.add(button);

        int x;
        x = 0;

        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                System.out.println("You CLicked the Button " + x + " times");  
                x = x + 1; // *getting error*
            }
        });
 
        frame.setVisible(true);
        frame.setSize(500,500);
        frame.setLocation(50,50);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

Answer 1

Your variable X needs to be a global, static variable because you never know when the registered ActionListener will be triggered. X is not in that scope and might be already removed at that time.

Answer 2

I strongly suggest using something like the following.

You shouldn't use global static variables for such a problem.

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class JavaApplication2 {
    public static void main(String[] args) {
        // TODO code application logic here
        JFrame frame = new JFrame();
        JPanel panel = new JPanel();
        JButton button = new JButton("Click");

        panel.setLayout(new FlowLayout());

        frame.add(panel);
        panel.add(button);

        Counter c = new Counter();

        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("You CLicked the Button " + c.getValue() + " times");
                c.increment();
            }
        });

        frame.setVisible(true);
        frame.setSize(500, 500);
        frame.setLocation(50, 50);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

}

class Counter {
    private int value = 0;

    void increment() {
        value++;
    }

    void reset() {
        value = 0;
    }

    public int getValue() {
        return value;
    }

    public void setValue(int value) {
        this.value = value;
    }

}