面试题05. 替换空格

请实现一个函数，把字符串 s 中的每个空格替换成"%20"。

示例 1：

输入：s = “We are happy.”
输出：“We%20are%20happy.”

解题代码

import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
* @Auther: truedei
* @Date: 2020 /20-5-6 22:46
* @Description:
*/
public class TestA {

static public String replaceSpace(String s) {
//1693648纳秒
return s.replaceAll("[ ]", "%20");

//1355205纳秒
return s.replace(" ","%20");

//636976纳秒
StringBuilder s1 = new StringBuilder();
for (int i = 0; i < s.length(); i++) {
if(s.charAt(i)==(char)' '){
s1.append("%20");
}else {
s1.append(s.charAt(i));
}
}
return s1.toString();

//594273纳秒
String s1="";
for (int i = 0; i < s.length(); i++) {
if(s.charAt(i)==(char)' '){
s1=s1+"%20";
}else {
s1=s1+s.charAt(i);
}
}
return s1;
}

}