[剑指]2空格替换

public static String replaceSpace(StringBuffer str) {
        StringBuffer sb=new StringBuffer();
        for(int i=0;i<str.length();i++){
            char c=str.charAt(i);
            if(c==' '){
                sb.append("%20");
            } else{
                sb.append(c);
            }
        }
        return sb.toString();
    }