Java int can't be changed because lambda expression must be final or effectively final

I am trying to make a Java tic tac toe game and am having some issues with the code.

What I want to do is just increment an int when the user clicks a button.

The problem is is that the compiler says "Error:local variables referenced from a lambda expression must be final or effectively final". What I understand this to mean is that I can only create an value and not redefine it in the same method but I am new to java and have no idea for a work around.

I am thinking of a work around by having multiple classes but this is overly complicated and I just want to add to the int like in python. If anyone has any idea on how to do this or a work around then it would be greatly appreciated.

Below is my program

public class TicTacToe extends Application {

    @Override
    public void start(Stage primaryStage) {
        //Some code here

        //this is Cerateing all the buttons
        //the buttons are formated in a 3X3 array for a total of 9 buttons
        Button B1 = new Button();
        //More buttons

        //this sets the size of the button

        //this is the int that tracks what button the user has pressed
        //this is my value
        int User = 0;

        //this gets if the user has clicked any of the buttons shold in therory do somthing
        B1.setOnAction((event) -> {
            B1.setText("X");
            //this is where I want to add to an value
            User++;
        });
        
        //More code

        System.out.println(User);
    }

}

You didn't specify where you got error, but this part should give an error:

int User = 0;

B1.setOnAction((event) -> {
    B1.setText("X");
    User++;
});

The User variable either needs to be a field, a wrapper like AtomicInteger or new int[1], or a final object. Here are a couple of ways to get around this. First of all, you can just make User a field.

private int User = 0;

Then don't declare it in the method. Another thing you can do is make a new int[1].

int User = new int[]{0};

B1.setOnAction((event) -> {
    B1.setText("X");
    User[0] ++;
});

Then when accessing it, you can use User[0]. Another way is using AtomicInteger. I don't really like it that much, but here is how you can use it anyways:

AtomicInteger User = new AtomicInteger(0);

B1.setOnAction((event) -> {
    B1.setText("X");
    User.incrementAndGet();
});