在位置 x 处将 char 添加到字符串中

Question

public String addLetter(char letter, int position, char[] word){
    char[]newWord = new char[word.length+1];

    if(position == 0){
        for(int i = position+1; i<word.length+1; i++){
            newWord[i] = word[i-1];
        }
        newWord[position] = letter;
    }else{

    }
    return new String(newWord);
}

我正在尝试创建一个方法，它将一个字母添加到一个字符串，然后返回它。到目前为止，我已经能够在字符串的前面添加一个字符，但我不太确定如何在中间/末尾添加一个字符。在 if 条件中，我将每个字母都推到后面一个槽，所以前面有新字母的空间。但是，如果我要在中间添加一些东西，我不知道该怎么办，有什么提示吗？

Answer 1

你可以像下面这样：

将你的char数组转换为字符串

   String b = new String("Tutorial");

然后创建 StringBuilder

   StringBuilder str = new StringBuilder(b);
   System.out.println("string = " + str);

   // insert character at offset 8
   str.insert(8, 's');

   // print StringBuilder after insertion
   System.out.print("After insertion = ");
   System.out.println(str.toString());// this will print Tutorials

Answer 2

最简单的方法是使用 2 个循环：

char[] newWord = new char[word.length + 1];

for(int i = 0; i < position; i++) newWord[i] = word[i];
newWord[position] = letter;
for(int i = position + 1; i < newWord.length; i++) newWord[i] = word[i - 1];

return new String(newWord);

Answer 3

使用 String.substring(int startindex, int end) 方法怎么样？

应该是这样的

    public static String addLetter(char letter, int position, String word){
    String toSupport = "";

    if(position == 0){
       toSupport += letter +word;
    } else {
        String temp = word.substring(0, position+1);
        toSupport += temp + Character.toString(letter) + word.substring(position+1, word.length());
    }
    return toSupport;
}

  public static void main(String[] args) {
     System.out.println(addLetter('a', 1, "hello"));
  }

Answer 4

你也可以这样：

public String addLetter(char letter, int position, char[] word) {
    return new StringBuilder(new String(word)).insert(position, letter).toString();
}

Answer 5

单循环，O(n) 复杂度

public String addLetter(char letter, int position, char[] word){
    char[]newWord = new char[word.length+1];

    int offset = 0;
    for(int i=0; i<newWord.length; i++) {
        if(position == i) {
            newWord[i] = letter;
            offset = 1;
        } else {
            newWord[i] = word[i-offset];
        }
    }

    return new String(newWord);
}

Answer 6

你可以像这样在不使用字符串操作 api 的情况下进行行移位

public String addLetter(char letter, int position, char[] word) {
        char[] newWord = new char[word.length + 1];
        int i;
        for (i = word.length; i >= position; i--) {
            newWord[i] = word[i-1];     
        }

        newWord[i] = letter;

        while(i>0){
            newWord[--i] = word[i];
        }

        return new String(newWord);
    }

Answer 7

private static String insertChar(String word, char letter, int position) {
        char[] chars = word.toCharArray();
        char[] newchars = new char[word.length() + 1];

        for (int i = 0; i < word.length(); i++) {
            if (i < position)
                newchars[i] = chars[i];
            else
                newchars[i + 1] = chars[i];
        }
        newchars[position] = letter;
        return new String(newchars);
    }

Answer 8

你可以这样做：

string = string.substring(0,x) + "c" + string.substring(x, string.length());