To be honest, these are just the tip of the iceberg in terms of both StringJoiner and Java 8 features. You can see the nice and clean IP address generated by supplying opening and closing brackets as prefix and suffix and dot as a separator. One of the common use cases of this feature is dynamically generating IP address as shown in our fourth example below: You can see in this example, we have enclosed the comma-separated String with an opening and closing braces by supplying them as prefix and suffix. Insurance: (Car Insurance,Health Insurance,Life Insurance) String text = new StringJoiner( ",", "(", ")") You can also provide prefix and suffix String to StringJoiner which can be used to enclose String like by giving parenthesis as prefix and suffix you can enclose String as shown in our third example below: If you are new to fluent API and interested in writing your own, you should check these Java design pattern courses on Udemy which talk about a software architecture approach for creating readable, intuitive, and easy-to-understand code. You can see how you can join multiple String in just one line using StringJoiner and fluent API. You can further shorten the above code in one line because StringJoiner allows fluent API as shown below: No need to call any function or write special logic, except adding String. In the case of StringBuffer or StringBuilder, you need to explicitly call the append(",") to join String by a comma but, here, once you tell StringJoiner about delimiter you are done. This code may look very similar to the code you may have written using StringBuffer but StringJoiner is very different from StringJoiner. You don't need to loop through a list of String anymore. You can see that StringJoiner has joined all String you have added to it. ( "comma separated String: " + text) Ĭomma separated String : Java,C + +,Python,Ruby StringJoiner joiner = new StringJoiner( ",") Creating a StringJoiner with delimiter as comma In this example, we join arbitrary String like Java, C++, Python, and Ruby to form a comma-separated String. Let's see our first example, which will join String by a comma to create a CSV String in Java 8 using the StringJoiner class. How to join String by a comma in Java 8 - Example You can further see these Java Functional Programming and Stream Courses to learn more about useful features like Lambda expression and Stream in a quick time. Though StringJoiner is just one of the hidden gems of the Java SE 8 release, there are many more day-to-day useful features that are hidden behind lambda expressions and streams like CompletableFuture. You don't need to write logic to start adding comma only after the first element and not to add after the last element, which Java programmers used to do while joining String in Java 6 or JDK 7. Well, you can certainly use the StringBuffer and StringBuilder class to join String in Java and that's what Java developers do prior to Java 8īut, StringJoiner provides a much cleaner and capable interface to join Strings. Some of the readers may be curious why do you need a new StringJoiner class if you already have StringBuffer and StringBuilder classes to concatenate String, which is nothing but joining. In this article, you will see some examples of StringJoiner to learn how to join String in Java 8. While creating the instance, you provide the delimiter, a String or character, which will be used between Strings while joining them like you can pass comma as a delimiter to create a comma-separated String or pipe to create a pipe-delimited String. In order to join Strings, you first create an instance of StringJoiner class. This class also allows you to specify a prefix and suffix while joining two or more String in Java. You can choose any delimiter to join String like comma, pipe, colon, or semi-colon. The can be used to join any number of arbitrary String, a list of String, or an array of String in Java. The Java 8 has added a new class called StringJoiner to join Strings. There are a lot of hidden gems on JDK 8 and I have uncovered many of them already in this blog and today we'll talk about one of such gems which you can use in your day-to-day programming activities like joining much String together. While everyone was looking at the lambda expression and Stream API, JDK quietly sneaked some of the exciting methods on its API.
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