Java 8, 11, 17 and 21 are Long-Term Support (LTS) releases, which most companies use in production. Since Java 9, a new version comes out every six months, and an LTS version every two years (every three years before Java 17). Each LTS bundles the features of the releases before it, so moving from 8 to 21 brings ten years of language, performance and security improvements.
Key Points: • Java 8 (2014): lambdas, Stream API, Optional, default methods, java.time. • Java 11 (2018): var in lambda parameters, new String methods (isBlank, strip, lines, repeat), the standard HttpClient, and running a single file with java Main.java. • Java 17 (2021): records, sealed classes, text blocks, switch expressions and pattern matching for instanceof. • Java 21 (2023): virtual threads, pattern matching for switch, record patterns and sequenced collections. • Java 25 (September 2025) is the newest LTS. Most interview questions still focus on 17 and 21. • Spring Boot 3 requires Java 17 or later, which is the main reason many projects are upgrading now.
Code Example:
import java.util.List;
public class ModernJavaTour {
record Employee(String name, String role, int salary) {} // Java 16+
public static void main(String[] args) {
var team = List.of( // Java 10+
new Employee("Asha", "DEV", 90_000),
new Employee("Ravi", "QA", 70_000));
for (var e : team) {
String level = switch (e.role()) { // Java 14+
case "DEV" -> "Engineering";
case "QA" -> "Quality";
default -> "Other";
};
System.out.println(e.name() + " works in " + level);
}
String json = """
{"team": %d}
""".formatted(team.size()); // Java 15+
System.out.print(json);
}
}Output:
Asha works in Engineering Ravi works in Quality {"team": 2}
Good to Know: Interviewers usually want practical reasons to upgrade, not a list of versions. Mention less boilerplate (records, var, text blocks), better performance and garbage collectors (G1 improvements, ZGC), virtual threads for high-concurrency services, security updates, and the fact that Spring Boot 3 needs Java 17.
Interview Tip: A concise interview answer is:
"Java 8, 11, 17 and 21 are the long-term support releases. Java 8 brought lambdas and streams, 11 added the HttpClient and new String methods, 17 added records, sealed classes and text blocks, and 21 added virtual threads and pattern matching for switch. I'd upgrade for less boilerplate, better performance and security, and because Spring Boot 3 requires Java 17."
Next question: What is the var keyword in Java 10, and when should you avoid it?