Since Java switch from a (kind of) 3-years feature release cycle to 6 months, it is hard for me to track the most important changes. This cheat-sheet shall help me to quickly pick the right Java version. For an extensive list see e.g. Wikipedia.

This lists just the most important changes (from my point of view):

Java 12 (2019)

• Switch expressions (preview)

    String result = switch (new Random().nextInt(3)) {
        case 0 -> "zero";
        case 1 -> "one";
        case 2 -> "two";
        default -> "impossible";
    };

• Microbenchmark suite

Exhaustive feature list. See also Java 12: New Features

Java 11 (2018 - LTS)

• HTTP Client API (now standard)
• Launch single-file programs without explicit compilation: java HelloWorld.java
• Launch single-file programs with shebang (note that the file must not end with “.java”):

    #!/usr/bin/java --source 11
    public class HelloWorld {
      public static void main(String[] args) {
        System.out.println("Hello World");
      }
    }

• Removal of JavaEE packages: JAX-WS, JAXB, JAF, JTA, Common annotations (@Resource…)
• Removal of CORBA
• Removal of JavaFX

Exhaustive feature list

Java 10 (2018)

• Local variable type inference - the var keyword
• Docker container awareness (for calculating memory and CPU resources)

Exhaustive feature list. See also What’s new in Java 10, Guide to Java 10.

Java 9 (2017)

• Java modules (aka Project Jigsaw)
• HTTP Client API (incubation)
• Process API
• Private methods in interfaces
• JShell (read-evaluate-print loop)
• Multi-release jar files
• G1 (Garbage First) garbage collector is now default

Exhaustive feature list. See also Java 9 New Features.

Java 8 (2014 - LTS)

• Lambda expressions, functional interfaces
• Method references (e.g. String::toUppercase)
• Stream API
• Default and static methods on interfaces
• Optional type
• DateTime API

Exhaustive feature list. See also Java 9 New Features.