package StringJoiner_package; import java.util.StringJoiner; public class StringJoiner_demo2 { public static void main(String[] args) { //1、创建对象 StringJoiner sj = new StringJoiner(",", "[", "]"); //2、添加元素 sj.add("a").add("b").add("c").add("d"); int len = sj.length(); System.out.println(len);//9 //3、打印 System.out.println(sj);//[a,b,c,d] String str = sj.toString(); System.out.println(str);//[a,b,c,d] } }