Reverse Words in a String (Java)-优快云博客

本文链接：https://blog.youkuaiyun.com/tofu_jelly/article/details/43014851

本文介绍了一种用于反转字符串中单词顺序的算法实现。通过使用Java编程语言，文章详细解释了如何处理输入字符串，包括去除多余空白字符、合并多个空格为单个空格，并最终实现单词的反转。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

Given an input string, reverse the string word by word.

For example,
Given s = "the sky is blue",
return "blue is sky the".

click to show clarification.

Clarification:

What constitutes a word?
A sequence of non-space characters constitutes a word.
Could the input string contain leading or trailing spaces?
Yes. However, your reversed string should not contain leading or trailing spaces.
How about multiple spaces between two words?
Reduce them to a single space in the reversed string.

Source

public class Solution {
    public String reverseWords(String s) {
        if(s.length() == 0) return s;
        
        String[] a = s.split(" ");  //只会按空格分开，多个空格时，中间的空格也会被当做空存起来，打印a的长度会发现空也被算进去，但输出不了字符，也不输出空格
        if(a.length == 0) return "";  //只有空格的情况
        
        
        List<String> temp = new ArrayList<String>();
        
        for(int i = 0; i < a.length; i++){
        	if(!a[i].isEmpty())  //数组也有isEmpty方法，注意这里不能判断a[i]是否为空格，而应判断是否为空  
        		temp.add(a[i]);
        }
        
        Collections.reverse(temp);  //Collections.reverse(list) 将list的元素逆序 注意是逆序不是排序 Collections.sort是排序
        
        String b = new String();
        for(int i = 0; i < temp.size() - 1; i++){  //倒数第二个后有空格
        	b += temp.get(i) + " ";
        }
        b += temp.get(temp.size() - 1); //最后一个后没空格
        
        return b;
    }
}

Test

    public static void main(String[] args){
    	String s = " ab c   d ";
    	System.out.println(new Solution().reverseWords(s));
  
    }