package String;

//将一个字符串进行反转，将字符串中指定部分进行反转，比如"abcdefg"转换为"abfedcg"

import org.junit.Test;

public class StringDemo {

//方法一：将字符串转换为字符数组

public String reverse1(String str,int startIndex,int endIndex){

if(str != null){

char[] charArray = str.toCharArray();

for(int x = startIndex,y = endIndex;x < y;x++,y--){

char temp = charArray[x];

charArray[x] = charArray[y];

charArray[y] = temp;

}

return new String(charArray);

}else{

return null;

}

}

//方法二：使用字符串拼接

public String reverse2(String str,int startIndex,int endIndex){

String startString = str.substring(0,startIndex);

for(int i = endIndex;i >= startIndex;i--){

startString += str.charAt(i);

}

startString += str.substring(endIndex + 1);

return startString;

}

//方法三：使用StringBuilder或者StringBuffer来替代String

public String reverse3(String str,int startIndex,int endIndex){

StringBuilder builder = new StringBuilder(str.length());

builder.append(str.substring(0,startIndex));

for (int i = endIndex; i >= startIndex ; i--) {

builder.append(str.charAt(i));

}

builder.append(str.substring(endIndex + 1));

return new String(builder);

}

@Test

public void test(){

String str = "abcdefg";

System.out.println(reverse3(str, 2, 5));

}

}