题解 | 字符串变形

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param s string字符串
     * @param n int整型
     * @return string字符串
     */
    public static String trans(String s, int n) {
        boolean flag = false;// 判断最后一个字符是否为空格
        // 字符串 -> 字符数组
        char[] charArray = s.toCharArray();
        for (int i = 0; i < n ; i++) {
            if (Character.isLowerCase(charArray[i]))
                charArray[i] = Character.toUpperCase(charArray[i]);
            else if (Character.isUpperCase(charArray[i]))
                charArray[i] = Character.toLowerCase(charArray[i]);
            if (charArray[n - 1] == ' ') flag = true;

        }
        // 字符数组 -> 字符串
        s = new String(charArray);
        System.out.println(s);

        // 字符串 ->  字符串数组
        String[] strArray = s.split(" ");// 会将末尾空格漏掉
        if (strArray.length < 2) {
            return s;
        }
        String temp = "";
        for (int i = 0; i < strArray.length / 2; i++) {
            temp = strArray[i];
            strArray[i] = strArray[strArray.length - 1 - i];
            strArray[strArray.length - 1 - i] = temp;
        }
        s = String.join(" ", strArray);

        if (flag) s = " " + s;// 补上末尾空格
        return s;
    }
}