数组转String

List<String> list = Lists.newArrayList();
list.add("测试1");
list.add("测试2");
list.add("测试3");
System.out.println(list.toString());
String join = String.join(",", list);
System.out.println("join{}"+join);

String join2 = Joiner.on(",").join(list);
System.out.println("join{}"+join2);