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"反转为"abfedcg"
package com.klvchen.exer;
import org.junit.Test;
public class StringDemo {
/*
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"反转为"abfedcg"
方式一: 转化为 char[]
*/
public String reverse(String str, int startIndex, int endIndex){
if (str != null && str.length() != 0){
char[] arr = str.toCharArray();
for (int x = startIndex, y = endIndex; x < y; x++, y--){
char temp = arr[x];
arr[x] = arr[y];
arr[y] = temp;
}
return new String(arr);
}
return null;
}
//方式二: 使用 String 的拼接
public String reverse1(String str, int startIndex, int endIndex){
if (str != null){
String reverseStr = str.substring(0, startIndex);
for (int i = endIndex; i >= startIndex; i--){
reverseStr += str.charAt(i);
}
reverseStr += str.substring(endIndex + 1);
return reverseStr;
}
return null;
}
//方式三: 使用 StringBuffer/StringBuilder 替换 String
public String reverse2(String str, int startIndex, int endIndex){
if (str != null){
StringBuffer builder = new StringBuffer(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 builder.toString();
}
return null;
}
@Test
public void testReverse(){
String str = "abcdefg";
// String reverse = reverse(str, 2, 5);
// String reverse = reverse1(str, 2, 5);
String reverse = reverse2(str, 2, 5);
System.out.println(reverse);
}
}
![](https://img2020.cnblogs.com/blog/1334255/202109/1334255-20210901225350449-597339561.png)