Leetcode-Reverse Words in a String -java

题目：

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.

分析：

1.利用String split() 提取出每个单词

2.对于前缀“ ”和后缀“ ”进行处理

public class Solution {
public String reverseWords(String s) {
if(s == null || "".equals(s)){
return "";
}
String[] array = s.split(" ");
StringBuffer sb = new StringBuffer();
for(int i = array.length - 1; i >=0; i--){
if(!"".equals(array[i])){
sb.append(array[i]).append(" ");
}
}
return sb.length() == 0 ? "" : sb.substring(0, sb.length() - 1).toString();

}//reverseWords
}

PS：

“” 为empty String对象，分配一个空的内存空间;

null 为空对象不分配内存空间;

String[] array = “ ”.split(" ");

array.length = 0;

isEmpty(“ ”) is false;

array.length;

StringBuffer.length(); String.length();