请实现一个函数，将一个字符串中的字符串空格替换成“%20”.例如：“We Are Happy”转化后为“We%20Are%20Happy”
思路：把字符串转化成字符数组，判断这个字符是不是空格，如果是空格的话就拼接字符“%20”,否则就直接拼接字符数组中的值
package demo2;
public class Main {
public static void main(String[] args) {
String str = "We Are Happy";
String result = replaceSpace(str);
System.out.println(result);
}
public static String replaceSpace(String str){
StringBuffer sb = new StringBuffer();
char[] c = str.toCharArray();
for (int i=0;i<c.length;i++) {
if (c[i] == ' ') {
sb.append("%20");
} else {
sb.append(c[i]);
}
}
return sb.toString();
}
}