如何使用stringbuilder返回输入字符串的每n个字符串？

Question

例如

> HW2.nthWord(3, "zero one two three four five six seven")
"zero three six"

下面是我写的代码，但它没有用。我不知道该怎么做。

public static String nthWord(int number, String s4){
    int word = 0;
    StringBuilder builder4 = new StringBuilder();
    for(int i = 0; word <= number; i++){
      if(s4.charAt(i) !=  ' '){
        builder4.append(s4.charAt(i));
      }else if(s4.charAt(i) == ' '){
        word = word + 1;
      }if (word == number){
        builder4.append(s4.charAt(i));
     }
    }
    return builder4.toString();
    }

Answer 1

试试这个

public static String nthWord(int number, String s4) {
    StringBuilder builder4 = new StringBuilder();
    String[] ss = s4.split(" ");
    for (int i = 0; i * number <= ss.length; i++)
        builder4.append(ss[i * number]).append(" ");

    return builder4.toString().trim();
}