Java实现替换字符串中空格为两个#

public static void addChar(String s) {
    char[] a = s.toCharArray();
    int wordStart = 0;
    for (int i=0; i<a.length; ++i) {
      int j = i;
      if (a[j] == ' ') {
        int wordEnd = j;

        String x = s.substring(0, wordEnd);
        String y = s.substring(wordEnd+1, s.length());
        s = x+"##"+y;
        i = j+1;
        wordStart = j + 2;
      }
      a = s.toCharArray();
    }
    System.out.println(s);
  }

public static void main(String[] args) {
    String s = "hello world shi jian ni hao";
    addChar(s);
    String[] a = s.split(" ");
    String res = "";
    for (int i=0; i+1<a.length; i+=2) {
      if (i+1 != a.length-1) {
        res += (a[i] + "##" + a[i + 1] + "##");
      } else {
        res += (a[i] + "##" + a[i + 1]);
      }
    }
    System.out.println(res);
  }