java实现字符串反转的6种方法

package com.mplus;

import java.util.Stack;

/**
* Created by alex on 16-5-15.
*/
public class ReverseStringDemo {
    static String reverseM1(String str) {
        StringBuffer sb = new StringBuffer();
        for (int i = str.length() - 1; i >= 0; i --) {
            sb.append(str.charAt(i));
        }

        return sb.toString();
    }
    static String reverseM2(String str) {
        StringBuffer reverse = new StringBuffer();

        Stack stack = new Stack();
        for (int i = 0; i < str.length(); i ++) {
            stack.push(str.charAt(i));
        }

        while (!stack.isEmpty()) {
            reverse.append(stack.pop());
        }

        return reverse.toString();
    }

    static String reverseM3(String str) {
        StringBuffer sb = new StringBuffer(str);
        return sb.reverse().toString();
    }

    /**
     * 折半反转
     * @param str
     * @return
     */
    static String reverseM4(String str) {
        int start = 0;
        int end = str.length() - 1;

        char[] cArr = str.toCharArray();

        while(start < end) {
            char c = cArr[end];
            cArr[end] = cArr[start];
            cArr[start] = c;
            start ++;
            end --;
        }
        return new String(cArr);
    }

    /**
     * 采用异或
     * @param str
     * @return
     */
    static String reverseM5(String str) {
        char[] cArr = str.toCharArray();

        int start = 0, end = cArr.length - 1;

        for (;start < end; start ++, end --) {
            cArr[start] ^= cArr[end];//采用异或
            cArr[end] ^= cArr[start];
            cArr[start] ^= cArr[end];
        }

        return new String(cArr);
    }

    /**
     * 采用递归
     * @param str
     * @return
     */
    static String reverseM6(String str) {
        if (str.length() == 1) {
            return str;
        }

        return reverseM6(str.substring(1)) + str.substring(0,1);
    }

    public static void main(String[] args) {
        System.out.println(reverseM1("abcdef"));
        System.out.println(reverseM2("abcdef"));
        System.out.println(reverseM3("abcdef"));
        System.out.println(reverseM4("abcdef"));
        System.out.println(reverseM5("abcdef"));
        System.out.println(reverseM6("abcdef"));
    }
}