Java: Recursion and Passing by value

Question

I'm a bit confused regarding recursion in Java:

public int recursion(Board board2,int x){
    Board board1 = board2;
    if(x==3){
        System.out.println("End");
        return 0;
    }

    board1.fix(obj, Color.BLUE, x, 12);
    return recursion(board1, x+1);

}

This is just an example of putting an object inside a board. How can I make changes to board1, but not to the original board that I passed in as a parameter? Since outside the method, the Board that I passed as parameter is changed after the execution, and I don't understand why. I was reading that Java passes by value and not by reference. I want to make the program return to its previous state during the recursion and not change the real board.

EDIT

I tried it this way, but it still doesn't work:

public int recursion(Board board2,int x){
    try{
        board1 = (Board)board2.clone();
    }catch (Exception e){
        System.out.println("Error "+e);
    }
    if(x==3){
        System.out.println("End");
        return 0;
    }

    board1.fix(obj, Color.BLUE, x, 12);
    return recursion(board1, x+1);    
}

EDIT 2

Here's how I implemented the clone method

class Board extends JPanel implements Cloneable{
    // ...
    @Override
    protected Board clone() throws CloneNotSupportedException{    
       return(Board) super.clone();  
    } 
    // ...

EDIT 3

I still can't get it to work

class Board extends JPanel implements Cloneable{
    public Color[][] board; 

    @Override
    public Board clone(){ 
        Board board1 = new Board();
        board1.board = this.board;
        return board1;  
    }
    // ...
}   

Answer 1

In the method, the parameter board2 holds the same reference as the argument you passed into the method. And I guess you don't want it to be this way. You want a copy of the board with the same values but different references, so that the effects you make on the copy does not affect the argument you passed in. Am I right? (I can read your mind!)

The clone() method is the best to use in this situation! First, in the Board class, implement Cloneable.

public class Board implements Cloneable {

}

And then add the clone() method to it.

The implementation of it is roughly this:

1. Create a new instance of the class

2. Assign all the fields found in this to the new instance

3. return the new instance.