字符串反轉小Demo

package com.cgfz.thread;
public class Demo1 {
public static void main(String[] args) {
	System.out.println(reverse2("abdf"));
}
//-------------------------------------------------將adcd或者abcdf反轉爲badc或fdcba----------------------
//第一種反轉方法
public static String reverse1(String s) {
	 int length = s.length();
     String begain = "";
     String last = "";
     for (int i = 0; i < length/2; i++) {
    	 begain = s.charAt(i) + begain;
     }
     for (int j = length-1; j >length/2; j--) {
    	 last =  last + s.charAt(j)  ;
     }
     if(length % 2 == 0) {
    	 return begain  +  last + s.charAt(length/2);
     }else {
    	 return begain  +  s.charAt(length/2) + last;
     }
     
     }
//第二種反轉
public static String reverse2(String str) {
	Integer halflength = str.length() / 2;
	StringBuffer begain = new StringBuffer(str.substring(0, halflength));
	StringBuffer last = new StringBuffer(str.substring(str.length() % 2 == 0 ? halflength : halflength + 1, str.length()));
	if(str.length() % 2 != 0) {
		return begain.reverse().toString() + str.charAt(halflength) + last.reverse().toString();
	}else {
		return begain.reverse().toString() + last.reverse().toString();
	}
}
//第三種反轉
public static String reverse3(String str) {
	StringBuffer buffer = new StringBuffer(str);
	String result = buffer.reverse().toString();
	if(str.length() % 2 == 0) {
		return result.substring(str.length()/2, str.length()) + result.substring(0, str.length()/2);	
	}else {
		return result.substring(str.length()/2 + 1, str.length()) +str.charAt(str.length()/2) + result.substring(0, str.length()/2);	
	}
}
//--------------------將abcd或者abcdf反轉爲dcba或者fdcba--------------------------------
//第三種反轉
public static String reverse(String str) {
	String newString= "";
	for (int i = 0; i < str.length(); i++) {
		newString=newString+str.charAt(str.length()-1-i);
	}
	return newString;
}

//第四種反轉
public static String reverse4(String str) {
	return new StringBuffer(str).reverse().toString();
}
}