PascalsTriangleGenerator.java

class PascalsTriangleGenerator {

  int[][] generateTriangle(int rows) {
    if (rows < 0) {
      throw new IllegalArgumentException("Rows can't be negative!");
    }

    int[][] triangle = new int[rows][];

    for (int i = 0; i < rows; i++) {
      triangle[i] = new int[i + 1];
      triangle[i][0] = 1;
      for (int j = 1; j < i; j++) {
        triangle[i][j] = triangle[i - 1][j - 1] + triangle[i - 1][j];
      }
      triangle[i][i] = 1;
    }
    return triangle;
  }

}