java:当字符串为We Are Happy.经过替换之后的字符串为We%20Are%20Happy

方法一：

public class Solution {

    public String replaceSpace(StringBuffer str) {

     String a=str.toString();

          char[] b = a.toCharArray();

          StringBuilder sBuilder = new StringBuilder();

          for (char c : b) {

              if(c==' ') {

              sBuilder.append("%20");

              }else {

                 sBuilder.append(c);

            }

        }

         String e = sBuilder.toString();

         return e;

    }

}