简介
StringJoiner是java8新增的工具类，StringJoiner是依赖StringBuilder实现，性能和StringBuilder差不多，也是非线程安全的。
示例public static void main(String[] args) {
String res1 = String.join("-", "2020","11","11");
System.out.println(res1); //2020-11-11
String res2 = String.join("*", List.of("aa","bb","cc"));
System.out.println(res2);//aa*bb*cc
List list1= List.of("11","22","33","44");
String res3 = list1.stream()
.map(item->item)
.collect(Collectors.joining("-"));
System.out.println(res3);//11-22-33-44
List list2 = List.of(new Dept(10,"ACCOUNTING","NEWYORK"),
new Dept(20,"RESEARCH","DALLAS"),
new Dept(30,"SALES","CHICAGO"));
String res4 = list2.stream().map(item->item.getDname())
.collect(Collectors.joining(", ","{","}"));
System.out.println(res4); //{ACCOUNTING, RESEARCH, SALES}
StringJoiner sj1 = new StringJoiner(",");
sj1.add("zhangsan");
sj1.add("lisi");
sj1.add("wanger");
System.out.println(sj1);// zhangsan,lisi,wanger
StringJoiner sj2 = new StringJoiner("/","C:/","/abc.txt").add("aa")
.add("bb")
.add("cc");
System.out.println(sj2); //C:/aa/bb/cc/abc.txt
}
结果： 
