Is there a way to update a variable outside a method that is used as a parameter in said method?

Question

I have 62 check boxes on 2 different panels. 30 of them on each panel are for selecting PC names while 1 on each selects all.

So on each of those 60 that are just selecting items I have this code:

private void HP04ActionPerformed(java.awt.event.ActionEvent evt) {                                     
        // TODO add your handling code here:
        setComponent(HP04, blrS,all_blr);

HP04 is the name of a checkbox for one of the PCs, blrS is the name of an int that counts how many checkboxes are selected(there is another int for the boxes on the other panel), all_blr is the name of the checkbox that selects all on the blr panel.

This is the method I used:

public void setComponent(javax.swing.JCheckBox  component, int room,javax.swing.JCheckBox  all)
    {
        System.out.println("Inside Component: "+component.isSelected()); //testing to see if the method is actually being called
        if (component.isSelected()){ //if checkbox is checked
            room++; //records how many boxes are checked
            if (room == 30)
            {
                all.setSelected(true);//autochecks "all" check box if all PCs are selected
            }
            if (!messagearea.getText().equals(""))
            {
                sendb.setEnabled(true);//if any boxes are checked and the message area is populated, enable the button
            }
        }
        else
        {
            room--;//records how many boxes are checked
            all.setSelected(false);//unchecks the "all" check box if not all of them are checked
            if (room == 0)
            {
                sendb.setEnabled(false);//disables button if no PCs are selected to be messaged
            }
        }
        System.out.println(room); //testing int updates based on UI changes
    }

Now the problem is room is only fetching the value of whatever variable is put in that parameter and then room itself is being modified. So in the example setComponent(HP04, blrS,all_blr); blrS is never changed.

I know the code inside the method works, it worked before I decided to cut down on code by using a method, as before I had the code inside the method in the actionperformed for every checkbox before hand... Like this:

private void HP04ActionPerformed(java.awt.event.ActionEvent evt) {                                     
        if (HP04.isSelected()){
            blrS++;
            if (blrS == 30)
            {
                all_blr.setSelected(true);
            }
            if (!messagearea.getText().equals(""))
            {
                sendb.setEnabled(true);
            }
        }
        else
        {
            blrS--;
            all_blr.setSelected(false);
            if (blrS == 0)
            {
                sendb.setEnabled(false);
            }
        }
        System.out.println(blrS);
    }         

It's just understanding how parameters and methods works that is tripping me up. It feels obvious that what I'm doing shouldn't work, room is a variable inside the method... But how do I change that?

Answer 1

Solution found:

"Why not return room from the method, and assign it to the variable when you call it? blrS = setComponent(HP04, blrS, all_blr);" – Rob Spoor (in the comments to this post)