Question

I’m doing an algorithm in Java using BlueJ as an IDE. I use trackback algorithm to solve the problem and everything works perfectly except for the checkstyle. The checkstyle errors are:

Assignment of parameter i is not allowed [on line 336] 
Assignment of parameter j is not allowed [on line 337]

However, as trackback requires the variables to be passed as the arguments and also be edited according to the situation, so I can’t do anything about this.

Does anybody know how to fix this? This is my code (error lines are commented):

 public boolean solve(int i, int j) {
        if (i == 9) {
            i = 0; // line 336
            if (++j == 9) { // line 337
                return true;
        }
        }
        ...
        for (int value = 1; value <= 9; ++value) {
            if (possible[value]) {  
                setCell(i,j,value);  
                if (solve(i+1,j)) {
                    return true;
                }
            }
        }
        game[i][j] = 0;
        return false;
}

Answer 1

You get a warning because Checkstyle considers that modiying method arguments is a bad practice. Either ignore it (or change the checkstyle config) if you don’t consider it as bad practice, or change the code to work on copies of the arguments:

public boolean solve(int iIndex, int jIndex) {
    int i = iIndex;
    int j = jIndex;
    // same code as before
}