Java：用类方法实现字符串的拼接

public class ChangeArgs_Exer01 {
    public static void main(String[] args) {
        StringUtil s=new StringUtil();
        String x=s.concat(',', "hello","world","my","baby");
        System.out.println(x);
    }
}
class StringUtil{
    public String concat(char oper, String... str){
        String x="";
        for (int i=0;i<str.length;i++){
            x+=str[i]+oper;

        }
        return x;
    }
}