Question

I’m getting an error that I really can’t explain when trying to compile my Java code:

error: constructor MinimaxThread in class MinimaxThread cannot be applied to given types;
        MinimaxThread mmt = new MinimaxThread(board.clone(), 2, true);
                            ^
  required: no arguments
  found: MCBoard,int,boolean
  reason: actual and formal argument lists differ in length

The error makes no sense, as I have a constructor that takes an MCBoard, int, and boolean:

public class MinimaxThread implements Runnable {
    public MCBoard board;
    public int depth;
    public HashMap<Tuple, Integer> moveEvals;
    boolean cont = true;
    boolean verbose = false;

    public MinimaxThread(MCBoard board, int initialDepth, boolean verbose) {
        this.board = board;
        depth = initialDepth;
        moveEvals = new HashMap<Tuple, Integer>();
        for (Tuple t : board.legalMoves) {
            moveEvals.put(t, new Integer(0));
        }
        this.verbose = verbose;
    }

It’s an overloaded constructor (there is one with just MCBoard and one with MCBoard and int), but I don’t see how that would matter. Any ideas? Here’s the calling code:

public static void testMinimax(){
    MCBoard board = new MCBoard();
    board.move(5,0);
    board.move(4,0);
    board.move(5,2);
    MinimaxThread mmt = new MinimaxThread(board.clone(), 2, true);
    mmt.run();
}

edit: board.clone() is overridden:

public MCBoard clone() {
    // irrelevant code removed
    return new MCBoard(gridClone, turn, legalMovesClone, moveListClone);
}

edit #2: Here is my git repository, for reproducibility:
https://github.com/cowpig/MagneticCave

Answer 1

EDIT: Now that you’ve given us your github URL, we can see what MinimaxThread really looks like – at least in the latest pushed code:

public class MinimaxThread extends Thread {
    public MCBoard board;
    public int depth;

}

Yup, I can see why the compiler would complain at that constructor call…

EDIT: Before we knew that MCBoard.clone() was overridden, the answer below made sense. Now, however, I can see no reason why the compiler should complain. Indeed, using the code you’ve given (but ignoring the actual implementation, which is irrelevant) it all compiles fine:

MinimaxThread.java:

public class MinimaxThread implements Runnable {
    public MinimaxThread(MCBoard board, int initialDepth, boolean verbose) {
    }

    public void run() {
    }
}

MCBoard.java:

public class MCBoard {
    public MCBoard clone() {
        return null;
    }
}

Test.java:

public class Test {
    public static void main(String[] args) throws Exception {
        MCBoard board = new MCBoard();
        MinimaxThread mmt = new MinimaxThread(board.clone(), 2, true);
    }
}

So I suspect you’re not building the code you’ve presented. Try to build the code above, and if that works, see if you can figure out the difference between that and your actual code.

Original answer

Presumably the compiler “thinks” that board.clone() returns Object, because that’s what’s declared by Object.clone(). So you need to cast the result to MCBoard:

MinimaxThread mmt = new MinimaxThread((MCBoard) board.clone(), 2, true);

Alternatively, you could override clone() within MCBoard, declaring that it returns MCBoard rather than Object.