How to Write Java 11 Code that is Compatible with Java 8?

How can I write code using Java 11 features but ensure compatibility with Java 8 and above?

javac --release 8 App.java

In Java development, ensuring backward compatibility can be challenging due to differences in language features and bytecode versions. If you're writing a library that you want to be compatible with Java 8 while leveraging Java 11 features, you can use the `--release` flag while compiling. This offers a way to specify both the source and target version, effectively allowing you to use Java 11 APIs while keeping the bytecode compatible with Java 8.

javac --release 8 App.java

Causes

• Using features introduced in Java versions later than 8, such as `var` in lambda expressions or new methods in standard APIs.
• Compiling with a higher source version than your target runtime allows.

Solutions

• Use the `javac --release 8` command instead of `-source 11 -target 1.8` to compile your code. The `--release` option automatically sets the appropriate source, target, and bootclasspath.
• Avoid using features only available in Java 9 and above if you want your library to be fully compatible with Java 8. Refer to the Java documentation for a complete list of changes and new features introduced in each version.
• If you are using a build tool like Maven or Gradle, configure the source and target compatibility settings accordingly: - For Maven, use <maven-compiler-plugin>: <configuration> <source>11</source> <target>8</target> </configuration> - For Gradle, set: dependencyManagement { imports { mavenBom "org.springframework.boot:spring-boot-dependencies:2.5.4" } } compileJava { sourceCompatibility = '11' targetCompatibility = '8' }

Mistake: Using the `-source` and `-target` flags without `--release` leads to unsupported bytecode versions.

Solution: Use the `--release` flag to automatically set the correct target version along with necessary boot classpath adjustment.

Mistake: Forgetting to check the Java version features before coding.

Solution: Refer to the official Java documentation for available features in each version to ensure compatibility.