Accessing a variable from constructor to actionPerformed method

Question

I have a variable ("data") that comes through into the JFrame through the constructor. I also have a button with an ActionPerformed method attached to it. I need to be able to access the variable "newData" from inside the ActionPerformed:

public JFrame(int data) {
    initComponents();
    
    int newData = data + 5;
}

private void ButtonActionPerformed(java.awt.event.ActionEvent evt) {                                             
    System.out.println(newData);
}  

How can I achieve this?

Answer 1

Move the declaration (the part with the type, int here) outside of the method. This makes newData an instance field rather than a local variable, and it is now accessible outside of the method (or in this case constructor).

public class MyJFrame extends JFrame {

    private int newData;

    public MyJFrame(int data) {
        initComponents();
        newData = data + 5;
    }
    
    private void ButtonActionPerformed(java.awt.event.ActionEvent evt) {                                             
        System.out.println(newData);
    }