题解 | #字符串变形#

import java.util.*;
import java.util.Stack;

public class Solution {
    public String trans(String s, int n) {
        // write code here

        Stack<String> stack = new Stack<>();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == ' ') {
                stack.push(sb.toString());
                stack.push(" ");
                sb = new StringBuilder();
                continue;
            }

            sb.append(convert(s.charAt(i)));
        }

        if (sb.length() != 0) {
            stack.push(sb.toString());
        }

        sb = new StringBuilder();
        while (!stack.isEmpty()) {
            sb.append(stack.pop());
        }

        return sb.toString();
    }

    private char convert(char dataChar) {
        if (Character.isUpperCase(dataChar)){
            dataChar = Character.toLowerCase(dataChar);
        }else if (Character.isLowerCase(dataChar)){
            dataChar = Character.toUpperCase(dataChar);
        }
        return dataChar;
    }
}