作业帮：字符串反转(头部插入)

题目描述：

不借助内置函数实现字符串反转

输入

I am a student.

输出
.tneduts a ma I

代码：

import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.nextLine();
        int length = str.length();
        String reverse = "";
        for (int i = 0; i < length; i++) {
            reverse = str.charAt(i) + reverse;
        }
        System.out.println(reverse);
    }
}

还有很多

方法一：（利用递归实现）

    public static String reverse1(String s) {
      int length = s.length();
      if (length <= 1)
       return s;
      String left = s.substring(0, length / 2);
      String right = s.substring(length / 2, length);
      return reverse1(right) + reverse1(left);  //调用递归
     }


方法二：（拼接字符串）

    public static String reverse2(String s) {
      int length = s.length();
      String reverse = "";
      for (int i = 0; i < length; i++)
       reverse = s.charAt(i) + reverse;
      return reverse;
     }


方法三：（利用数组，倒序输出）

    public static String reverse3(String s) {
      char[] array = s.toCharArray();
      String reverse = "";
      for (int i = array.length - 1; i >= 0; i--)
       reverse += array[i];
      return reverse;
     }


方法四：（利用StringBuffer的内置reverse方法）

    public static String reverse4(String s) {
      return new StringBuffer(s).reverse().toString();
     }


方法五：（利用临时变量，交换两头数值）

    public static String reverse5(String orig) {
      char[] s = orig.toCharArray();
      int n = s.length - 1;
      int halfLength = n / 2;
      for (int i = 0; i <= halfLength; i++) {
       char temp = s[i];
       s[i] = s[n - i];
       s[n - i] = temp;
      }
      return new String(s);
     }


方法六：（利用位异或操作，交换两头数据）

    public static String reverse6(String s) {
      
      char[] str = s.toCharArray();
      
      int begin = 0;
      int end = s.length() - 1;
      while (begin < end) {
       str[begin] = (char) (str[begin] ^ str[end]);
       str[end] = (char) (str[begin] ^ str[end]);
       str[begin] = (char) (str[end] ^ str[begin]);
       begin++;
       end--;
      }
      return new String(str);
     }


方法七：（利用栈结构）

    public static String reverse7(String s) {
      char[] str = s.toCharArray();
      Stack<Character> stack = new Stack<Character>();
      for (int i = 0; i < str.length; i++)
       stack.push(str[i]);
      
      String reversed = "";
      for (int i = 0; i < str.length; i++)
       reversed += stack.pop();
      
      return reversed;
     }