字符逆序（一）

package test;

import java.util.Scanner;

/* 一个句子单词逆序、句子逆序
*/
public class exam09 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            String str = scanner.nextLine();
            reverseAll1(str);
            reverseAll2(str);
            reverseAll3(str);
        }
    }

    public static void reverseAll1(String str) {
        // 方法一
        char[] chars = str.toCharArray();
        for (int i = 0, j = chars.length - 1; i <= j; i++, j--) {
            // 两个指针，i向后，j向前
            char temp = chars[i];
            chars[i] = chars[j];
            chars[j] = temp;
        }
        System.out.println(String.valueOf(chars));
    }

    public static void reverseAll2(String str) {
        // 方法二
        StringBuilder sb = new StringBuilder(str);
        sb.reverse();
        System.out.println(sb.toString());
    }

    public static void reverseAll3(String str) {
        // 方法三
        StringBuilder sb = new StringBuilder();
        for (int i = str.length() - 1; i >= 0; i--) {
            sb.append(str.charAt(i));
        }
        System.out.println(sb.toString());
    }
}