Java

Variables

final String name = "Ada"; // immutable reference
int age = 25;
var message = "Hello";     // type inferred (Java 10+)

Classes

public class User {
    private final String name;

    public User(String name) {
        this.name = name;
    }

    public void greet() {
        System.out.println("Hello, " + name);
    }
}

Collections

List<String> names = List.of("Ada", "Grace");

List<Integer> result = numbers.stream()
    .filter(n -> n > 0)
    .map(n -> n * 2)
    .toList();

Modern Java

record User(String name, int age) {}

String status = switch (code) {
    case 200 -> "OK";
    default -> "Unknown";
};

Version Management

• Prefer LTS versions such as Java 17, 21, or 25.
• Use SDKMAN! to manage multiple JDK versions.
• Configure Java toolchains in Gradle or Maven.
• Prefer ./gradlew and ./mvnw over globally installed build tools.

sdk install java 21-tem
sdk use java 21-tem
java --version

References

• Java Documentation
• Dev.java
• SDKMAN!