Both StringJoiner and String.join offer efficient ways for concatenating strings with delimiters, with StringJoiner providing additional flexibility for prefixes and suffixes.
Source Code
StringJoiner sj = new StringJoiner(", ", "{", "}");
sj.add("one").add("two").add("three");
System.out.println(sj.toString()); // Outputs: {one, two, three}
String result = String.join("-", "2017", "10", "31");
System.out.println(result); // Outputs: 2017-10-31