字符串与字符串数组、字符串集合之间的转换

//字符串-->字符串数组
String str = "11,22";
String[] split = str.split(",");
String strArr = Arrays.toString(split);

//字符串数组-->字符串
String[] strArr2 = {"AA","BB","CC"};
String str2 = String.join(",",strArr2);

//字符串集合-->字符串
List<String> list = new ArrayList<>();
list.add("AA");
list.add("BB");
list.add("CC");
String str3 = String.join(",", list);

String join = StringUtils.join(list, '_');