How do we simplify this kind of code in Java? Something like macros in C?

Question

public static boolean diagonals(char[][] b, int row, int col, int l) {

            int counter = 1; // because we start from the current position
            char charAtPosition = b[row][col];
            int numRows = b.length;
            int numCols = b[0].length;
            int topleft = 0;
            int topright = 0;
            int bottomleft = 0;
            int bottomright = 0;
            for (int i=row-1,j=col-1;i>=0 && j>=0;i--,j--) {
                if (b[i][j]==charAtPosition) {
                    topleft++;
                } else {
                    break;
                }
            }
            for (int i=row-1,j=col+1;i>=0 && j<=numCols;i--,j++) {
                if (b[i][j]==charAtPosition) {
                    topright++;
                } else {
                    break;
                }
            }
            for (int i=row+1,j=col-1;i<=numRows && j>=0;i++,j--) {
                if (b[i][j]==charAtPosition) {
                    bottomleft++;
                } else {
                    break;
                }
            }
            for (int i=row+1,j=col+1;i<=numRows && j<=numCols;i++,j++) {
                if (b[i][j]==charAtPosition) {
                    bottomright++;
                } else {
                    break;
                }
            }
            return topleft + bottomright + 1 >= l || topright + bottomleft + 1 >= l; //in this case l is 5
    }

After I was done posting the code above here, I couldn't help but wanted to simplify the code by merging the four pretty much the same loops into one method.

Here's the kind of method I want to have:

public int countSteps(char horizontal, char vertical) {
   
}

Two parameters horizontal and vertical can be either + or - to indicate the four directions to walk in. What I want to see if possible at all is i++; is generalized to i horizontal horizontal; when horizontal taking the value of +.

What I don't want to see is if or switch statements, for example:

public int countSteps(char horizontal, char vertical) {
     if (horizontal == '+' && vertical == '-') {
         for (int i=row-1,j=col+1;i>=0 && j<=numCols;i--,j++) {
                if (b[i][j]==charAtPosition) {
                    topright++;
                } else {
                    break;
                }
            }
     } else if (horizontal == '+' && vertical == '+') {
          for (int i=row+1,j=col+1;i>=0 && j<=numCols;i++,j++) {
                if (b[i][j]==charAtPosition) {
                    topright++;
                } else {
                    break;
                }
            }
     } else if () {

     } else {

     }
}

Since it is as tedious as the original one. Note also that the comparing signs for the loop condition i>=0 && j<=numCols; for example, >= && <= have correspondence with the value combination of horizontal and vertical.

Sorry for my bad wording, please let me know if anything is not clear.

Answer 1

You can easily convert the loops to something like:

int doit(int i_incr, int j_incr) {
    int cornerIncrement = 0;
    for (int i=row+i_incr, j=col+j_incr; i>=0 && j>=0; i+=i_incr, j+=j_incr) {
        if (b[i][j]==charAtPosition) {
            cornerIncrement++;
        } else {
            break;
        }
    }
    return cornerIncrement;
}

And then repeat 4 times...

int increment = doit(+1, -1);  // Or (-1, +1) etc
topLeft += increment;  // Or bottomLeft/topRight/bottomRight

Answer 2

So you have these two loops:

for (int i=row-1,j=col-1;i>=0 && j>=0;i--,j--) {
  if (b[i][j]==charAtPosition) {
    topleft++;
  } else {
    break;
  }
}
for (int i=row-1,j=col+1;i>=0 && j<=numCols;i--,j++) {
  if (b[i][j]==charAtPosition) {
    topright++;
  } else {
    break;
  }
}

First, turn your counters into an array, i.e. topleft -> counter[0] and topright -> counter[1]

Then, turn the difference between the code into variables, so you have:

for(direction = 0; direction < 2; direction++) {
  int offset = direction * 2 - 1; // This is what I mean by doing some math
  for(int i=row-1,j=col+offset;i>=0 && -j*offset>=-numCols*direction;i--,j+=offset) {
  if (b[i][j]==charAtPosition) {
    counter[direction]++;
    // etc.

The math can get ugly sometimes, or you can do it in a separate line. Look at my other post on this question for an elegant way to do the math in this particular problem using ? : syntax.