java实现字符串反转

代码:

import java.util.Stack;

public class StringReverse {
    public static void main(String[] args) {
        String s = "hello";
        String ss = reverse7(s);
        System.out.println(ss);
    }

    // 使用内置类(StringBuilder或StringBuffer)
    public static String reverse1(String s) {
        // StringBuilder strBuilder = new StringBuilder(s);
        // String ret = strBuilder.reverse().toString();
        StringBuffer strBuf = new StringBuffer(s);
        String ret = strBuf.reverse().toString();
        return ret;
    }

    // 有左到右 拼接字符串
    public static String reverse2(String s) {
        String ret = "";
        for (int i = 0; i < s.length(); ++i) {
            ret = s.charAt(i) + ret;
        }
        return ret;
    }

    // 从右到左 拼接字符串
    public static String reverse3(String s) {
        String ret = "";
        for (int i = s.length() - 1; i >= 0; --i) {
            ret += s.charAt(i);
        }
        return ret;
    }

    public static String reverse4(String s) {
        String ret = "";
        char[] charArr = s.toCharArray();
        int len = charArr.length;
        for (int i = 0; i < len / 2; ++i) {
            char tmp = charArr[i];
            charArr[i] = charArr[len - 1 - i];
            charArr[len - 1 - i] = tmp;
        }
        ret = new String(charArr);
        return ret;
    }

    // 使用异或
    public static String reverse5(String s) {
        String ret = "";
        char[] charArr = s.toCharArray();
        int begin = 0, end = charArr.length - 1;
        while (begin < end) {
            charArr[begin] = (char) (charArr[begin] ^ charArr[end]);
            charArr[end] = (char) (charArr[begin] ^ charArr[end]);
            charArr[begin] = (char) (charArr[begin] ^ charArr[end]);

            begin++;
            end--;
        }
        ret = new String(charArr);
        return ret;
    }

    // 使用栈
    public static String reverse6(String s) {
        String ret = "";
        Stack<Character> stack = new Stack<Character>();
        for (int i = 0; i < s.length(); ++i) {
            stack.push(s.charAt(i));
        }
        while (!stack.isEmpty()) {
            ret += stack.pop();
        }

        return ret;
    }

       // 使用递归
    public static String reverse7(String s) {
        if (s.length() == 1)
            return s;
        return reverse7(s.substring(1)) + s.charAt(0);
    }
}