October 5, 2023

Introduction 

In this blog, we will discuss the features of Java 17 and how to upgrade an existing backend application operating on Java 8 to Java 17. From Java 8 to Java 17, there have been several improvements to the Java environment and the Java environment has changed tremendously from Java 8. The most notable change is the Java release cycle. Java 8 was published in 2014, and Java 17 was issued as the following Long-Term Support (LTS) release on September 21, 2021. The next LTS release will be Java 21 in 2023. There is a seven-year gap between the two releases. However, because Java is being updated every six months, you should expect a new version every six months. This is a big change for the Java ecosystem since it allows developers to have immediate access to the latest Java features. 

Java 17 New Features

1. Flexible main method
2. Records
3. Switch Expressions
4. Text blocks
5. Pattern matching for instanceof
6. Sealed Classes

1. Flexible Main Method

Java now supports numerous entry points to an application in contrast to the conventional “public static void main (String [] args),” allowing for greater flexibility and expressiveness in the creation and execution of programs. 

 2. Records

Records is a new feature that was introduced in Java 14.  You can make classes that are utilized to store data. Records are identical to POJO classes but need far less code because they don’t need any external libraries, unlike most developers who use Lombok to create POJO classes. In the sample below, you can see how little code is required to construct a record class. 

3. Switch Expression

In Java 17, you can return the full switch expression rather than utilizing the break keyword to exit the switch statement or the return keyword on each switch case to return a value. Instead, you can return the entire switch expression. This enhanced switch expression makes the overall code look much cleaner and easier to read. 

4. Text Blocks

Text blocks are a new feature that was added to Java 15. You can make multiline strings with it without the use of escape sequences. When constructing SQL queries or JSON strings, this is incredibly helpful. You can notice how much cleaner the code looks when utilizing text blocks in the example below. 

5. Pattern Matching for Instanceof

Pattern matching for instanceof is a new feature that was added to Java 16. You can use the instanceof operator as an expression to get the returned object from a casted object. When working with nested if-else statements, this is really helpful. You can see how the instanceof operator is used to catch the user object in the example below, instead of an explicit cast. 

6. Sealed Classes

Sealed classes are a new feature that was added to Java 17. It allows you to restrict the number of subclasses that a class or interface can inherit from. This is really beneficial when you wish to restrict the subclasses that can be inherited from a class or interface. The example below demonstrates how the sealed keyword is used to limit the number of subclasses that can inherit a class. 

How to upgrade from Java 8 to Java 17?

• Upgrade the Maven compiler plugin version

<plugin> 
    <groupId>org.apache.maven.plugins</groupId> 
    <artifactId>maven-compiler-plugin</artifactId> 
    <version>3.8.1</version> 
     <configuration> 
         <source>17</source> 
         <target>17</target> 
     </configuration> 
</plugin> 

You can use the mvn versions:display-dependency-updates command to check for dependency updates, and the output will look like this. 

• Change the JDK version for an Eclipse project

-> Open preferences in windows 

1. Change the JDK compliance level to 17 as shown below

2. Add JRE definition for the build path of the project as shown below

• Set Java environment path in Ubuntu

Run the below commands, get the location of JDK, and create the JAVA_HOME variable inside bashrc file as shown below.

JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64 

Export JAVA_HOME 

save the file and run the below command to refresh the current shell environment by running the bashrc file 

source ~/.bashrc 

Conclusion

In this blog, we’ve explored the exciting features of Java 17 and demonstrated how to smoothly upgrade your existing Java 8 backend application to the latest version. With enhancements like flexible entry points, records, switch expressions, text blocks, pattern matching, and sealed classes, Java 17 brings new levels of productivity and readability to your codebase. As Java’s release cycle continues to evolve, staying up-to-date with the latest features becomes more accessible, empowering developers to create efficient, modern applications.