如何为10 x 10网格按钮布局中的每个JButton提供唯一的ID /名称

Question

I am trying to give each JButton from a 10 x 10 button layout (so 100 buttons) each unique name or ID or number so I can call them later. I made an ArrayList because that's what some other person did.

public ArrayList<JButton> myList;

//Some other code

        for(int row = 0; row < 10; row++)
        {
            for(int col = 0; col < 10; col++)
            {
                    button = new JButton();
                    button.addActionListener( al );
                    myList.add(button);
                    for(JButton button : myList)
                        button.setText("");
                    panel_1.add(button);
            }
        }

The program compiles but it doesn't run. It's showing error at

myList.add(button);

It's a null pointer exception apparently.

but I don't know why. Is it not adding the buttons to the ArrayList? Also how do I give each button a unique name or string?

Answer 1

The program compiles but it doesn't run. It's showing error at

The ArrayList is null because you didn't create an ArrayList object.

The code should be:

private ArrayList<JButton> myList = new ArrayList<JButton>();

Also how do I give each button a unique name or string?

There is no need to give the button a unique name. Its unique name is the "index" used to access the JButton in the ArrayList .

You probably don't even need the ArrayList.

Normally you add an ActionListener to the button. Then you can just use the getSource() method of the ActionEvent to get the reference to the button.