两个循环就可以解决

 public static void main(String[] args) {
        //99乘法表
        int n;
        for (int a = 1; a <= 9; a++) {
            for (int b = 1; b <= a; b++) {
                n = a * b;
                System.out.printf("%d*%d=%2d ", a, b, n);
            }
            System.out.println();

        }
    }