例如输入：I love programming

输出：I evol gnimmargorp

算法思路就是：根据空格提取每一个单词，存放在一个buffer里进行翻转处理，再添加到新的字符串。最后新的字符串就完成整个方法过程。

public class ReserveString {
	public String reserve(String sentence){
		String backS = new String();
		StringBuffer temp = new StringBuffer();
		 
		int i=0;
		
			while (i<sentence.length()-1 && sentence.charAt(i)!=' '){
				temp.append(sentence.charAt(i));
				i++;
				
				if (i==sentence.length()-1 || sentence.charAt(i)==' '){
					if (i==sentence.length()-1) {temp.append(sentence.charAt(i));}
					int ii=temp.length()-1;
					int jj=0;
					while (ii-jj>=0){
						char Sii=temp.charAt(ii);
						char Sjj=temp.charAt(jj);
						temp.setCharAt(ii,Sjj);
						temp.setCharAt(jj,Sii);
						ii--;jj++;
					}//得到单个单词并反转
					
					i++; //跳过空格
					backS=backS+temp+" "; //添加翻转后单词和空格
					temp = new StringBuffer(); //重置temp存放单个单词
				}
			}
		return backS;
	}
	
	public static void main(String[] args) {
		ReserveString reserveString = new ReserveString();
		System.out.println(reserveString.reserve("I love programming rly"));
	}
}