Spiral Matrix II

public class SpiralMatrix {
    public int[][] generateMatrix(int n) {
        int[][] spiral = new int[n][n];

        if(n == 0) {
            return spiral;
        }

        int rowStart = 0;
        int colStart = 0;
        int rowEnd = n - 1;
        int colEnd = n -1;
        int number = 1;

        while(rowStart <= rowEnd && colStart <= colEnd) {
            for(int i = colStart; i <= colEnd; i++) {
                spiral[rowStart][i] = number++;
            }

            rowStart++;

            for(int i = rowStart; i <= rowEnd; i++) {
                spiral[i][colEnd] = number++;
            }

            colEnd--;

            for(int i = colEnd; i >= colStart; i--) {
                if(rowStart <= rowEnd) {
                    spiral[rowEnd][i] = number++;
                }
            }

            rowEnd--;

            for(int i = rowEnd; i >= rowStart; i--) {
                if(colStart <= colEnd) {
                    spiral[i][colStart] = number++;
                }
            }

            colStart++;
        }

        return spiral;
    }
}