How Can I Efficiently Create Comma-Delimited Lists in Java?

Efficiently Creating Delimited Lists in Java

In Java, it's often necessary to create comma-delimited lists of values. While a naive approach may suffice, it can be inefficient due to repeated string creation. Fortunately, there are more efficient alternatives.

Pre-Java 8:

Apache Commons Lang provides the StringUtils.join method, which offers a convenient way to join elements into a delimited string:

String joinedString = StringUtils.join(new String[] {"elementName", "anotherElementName"}, ",");

Java 8:

Java 8 introduced several new methods for efficient string joining:

• StringJoiner: A mutable sequence of characters that can be efficiently joined together.

StringJoiner joiner = new StringJoiner(",");
joiner.add("elementName").add("anotherElementName");
String joinedString = joiner.toString(); // "elementName,anotherElementName"

• String.join: A static method that joins the elements of a varargs list or an iterable.

String joinedString = String.join(",", "elementName", "anotherElementName"); // "elementName,anotherElementName"

List<String> strings = List.of("Java", "is", "cool");
String joinedString = String.join(" ", strings); // "Java is cool"

These methods provide a concise and efficient way to build delimited lists in Java, greatly reducing the overhead of string concatenation.

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