java字元串大小寫字母互改

import java.util.Scanner;

public class Test {
    /**
     * 測試數據
     * 
     * @param args
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        System.out.println(ExchangeStringA(s));
        System.out.println(ExchangeStringB(s));
    }

    /**
     * 方式一
     * 
     * @param s
     * @return
     */
    public static String ExchangeStringA(String s) {
        StringBuffer result = new StringBuffer();
        String lowerString = s.toLowerCase();    //這兩步
        String upString = s.toUpperCase();        //是關鍵
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == lowerString.charAt(i)) {
                result.append(upString.charAt(i));
            } else {
                result.append(lowerString.charAt(i));
            }
        }
        return result.toString();
    }

    /**
     * 方式二 以字母的ascii碼來操作 大小寫之間相差32 
     * a-z：97-122 
     * A-Z：65-90
     * @param s
     * @return
     */
    public static String ExchangeStringB(String s) {
        char c[] = s.toCharArray();
        for (int i = 0; i < c.length; i++) {
            if (c[i] >= 65 && c[i] <= 90) {
                c[i] = (char) (c[i] + 32);
            } else {
                c[i] = (char) (c[i] - 32);
            }
        }
        return String.valueOf(c);
    }
}