print pascal's triangle

package com.example;
import java.util.*;
public class Main {
  private static HashMap<Integer, HashMap<Integer, Integer>> memoize;
//  private static int combinanation_no_memoize(int n, int k) {
//    if (k  == 0 | k == n) { return 1;
//    return combinanation_no_memoize(n - 1, k -1) +
//      combinanation_no_memoize(n - 1, k);
//    }
//  }
  private static int combination(int n, int k) {
    if (memoize == null) {
      memoize = new HashMap<Integer,HashMap<Integer,Integer>>();
      memoize.put(0,new HashMap<Integer, Integer>());
      memoize.get(0).put(0, 1);
    }
    if (!memoize.containsKey(n)) {
      memoize.put(n, new HashMap<Integer, Integer>());
      memoize.get(n).put(0, 1); memoize.get(n).put(n, 1);
    }
    if (!memoize.get(n).containsKey(k) || k > 0 && k < n) {
      int ret = combination(n - 1, k - 1) + combination(n - 1, k);
      memoize.get(n).put(k, ret); return ret;
    }
    return memoize.get(n).get(k);
  }
  private static String leading_space(int row, int number) {
    StringBuilder sb = new StringBuilder();
    for (int i = number; i > row; i--) {
      sb.append("*");
    }
    return sb.toString();
  }
  private static void print_pascal_triangle(int number) {
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i <= number; i++) {
      sb.append(leading_space(i, number));
      for (int j = 0; j <= i; j++) {
        sb.append(combination(i, j));
        if (j == i) { break; }
        sb.append("-");
      }
      sb.append("\n");
    }
    System.out.print(sb);
  }
  public static void main(String[] args) {
    print_pascal_triangle(10);
//    System.out.println(memoize);
  }
}