Word swapping in Java implementation strings

Suppose the string is "Hello world!" and now you want to change it to "! World Hello "
problem : The difficulty of this problem is how to ensure that the word is not reversed when the string is reversed
Problem Solving :

The first method of solution. First, the word is reversed, and then the string is reversed;
The second method of solution. First, the string is reversed, and then the word is reversed;

This is only the second solution:
* Core Code section: * *

public  void reverse(String s){        StringBuffer stringBuffer = new StringBuffer(s);        String a = stringBuffer.reverse().toString();//将字符串逆置        String[] b = a.split("\\s+");//分理出其中的非空格部分        stringBuffer = new StringBuffer();        for(String c:b){            StringBuffer stringBuffer1 = new StringBuffer(c);            stringBuffer.append(" "+stringBuffer1.reverse.toString());//此处双引号里面的空格不可少        }        System.out.print(stringBuffer.toString());    }

Word swapping in Java implementation strings