Java 17+ Interview Questions and Answers

Java 17+ Interview Questions and Answers (Latest LTS)

Java 17 is a Long-Term Support (LTS) release and is widely adopted in enterprise applications. Interviewers now expect candidates to understand not just core Java, but also modern language features introduced from Java 8 to Java 17+.

This article covers conceptual, practical, and scenario-based Java 17+ interview questions with answers.

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1. What is Java 17 and why is it important?

Answer:

Java 17 is an LTS (Long-Term Support) release, meaning it receives updates and security fixes for many years.

Why Java 17 matters:

• Stable for enterprise production systems
• Includes features from Java 9 → Java 17
• Improved performance, security, and readability
• Preferred baseline for Spring Boot 3+

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2. What are LTS versions in Java?

Answer:

LTS (Long-Term Support) versions receive extended maintenance.

Java LTS versions:

• Java 8
• Java 11
• Java 17
• Java 21 (latest LTS)

Interview Tip: Companies usually migrate only to LTS versions.

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3. What are Records in Java? (Java 16+)

Answer:

Records are a special type of class used to store immutable data.

Example:

public record User(String name, int age) {}

What Java generates automatically:

• Constructor
• getters
• equals(), hashCode()
• toString()

Benefits:

• Less boilerplate code
• Immutable by default
• Perfect for DTOs

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4. Can records have methods?

Answer:

✅ Yes.

public record User(String name, int age) {
    public boolean isAdult() {
        return age >= 18;
    }
}

❌ But records cannot extend classes, only implement interfaces.

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5. What is Sealed Class in Java? (Java 17)

Answer:

Sealed classes restrict which classes can extend them.

Example:

public sealed class Shape permits Circle, Rectangle {}

Allowed subclasses:

public final class Circle extends Shape {}
public non-sealed class Rectangle extends Shape {}

Use cases:

• Domain-driven design
• Controlled inheritance
• Better pattern matching

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6. Difference between sealed, non-sealed, and final

Keyword	Meaning
sealed	Restricts subclasses
non-sealed	Opens inheritance again
final	No inheritance allowed

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7. What is Pattern Matching for instanceof?

Answer:

Pattern matching removes explicit casting.

Before Java 16:

if (obj instanceof String) {
    String s = (String) obj;
}

Java 16+:

if (obj instanceof String s) {
    System.out.println(s.length());
}

Benefits:

• Cleaner code
• Fewer bugs
• Better readability

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8. What is Switch Expression? (Java 14+)

Answer:

Switch can now return values.

Example:

int result = switch(day) {
    case 1, 7 -> 0;
    case 2, 3, 4, 5, 6 -> 1;
    default -> throw new IllegalStateException();
};

Advantages:

• No fall-through
• Concise syntax
• Expression-based

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9. Difference between switch statement and switch expression

Switch Statement	Switch Expression
No return value	Returns a value
Uses break	Uses ->
Error-prone	Safer

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10. What is Text Block in Java? (Java 15+)

Answer:

Text blocks allow multi-line strings.

Example:

String json = """
{
  "name": "John",
  "age": 25
}
""";

Benefits:

• Readable SQL/JSON/HTML
• No escaping required

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11. What is the Java Module System? (Java 9)

Answer:

Modules allow you to group packages and control access.

Example:

module com.example.app {
    requires java.sql;
    exports com.example.service;
}

Advantages:

• Strong encapsulation
• Better dependency management
• Smaller runtime images

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12. What is var in Java? Is it dynamically typed?

Answer:

var is local variable type inference, not dynamic typing.

var list = new ArrayList<String>();

Important points:

• Type is decided at compile-time
• Cannot be used for fields or method parameters
• Improves readability

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13. What is jlink?

Answer:

jlink creates a custom lightweight Java runtime.

Benefits:

• Smaller application size
• Faster startup
• Only required modules included

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14. What is jpackage? (Java 14+)

Answer:

jpackage creates native installers.

Supported formats:

• .exe (Windows)
• .deb / .rpm (Linux)
• .pkg (macOS)

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15. What is Foreign Function & Memory API? (Java 17 Incubator)

Answer:

Allows Java to interact with native memory and C libraries safely without JNI.

Benefits:

• Faster native calls
• Safer memory handling
• Replacement for JNI

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16. How is Garbage Collection improved in Java 17?

Answer:

Java 17 improves:

• G1 GC (default)
• Lower pause times
• Better memory efficiency

Removed obsolete collectors:

• CMS (Concurrent Mark Sweep)

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17. What security improvements exist in Java 17?

Answer:

• Strong encapsulation of JDK internals
• Deprecated Security Manager
• Better cryptography defaults
• Improved TLS support

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18. Is Java still relevant after Java 17?

Answer:

✅ Absolutely.

Reasons:

• Strong enterprise ecosystem
• Spring Boot 3 uses Java 17
• High performance
• Massive community support

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19. Java 17 vs Java 8 – Key Differences

Feature	Java 8	Java 17
Records	❌	✅
Sealed Classes	❌	✅
Switch Expressions	❌	✅
Text Blocks	❌	✅
Module System	❌	✅

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20. What Java 17 topics should you focus on for interviews?

Must-know topics:

• Records
• Sealed classes
• Pattern matching
• Switch expressions
• Modules
• JVM & GC basics
• Performance improvements

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Final Thoughts

Java 17 is not just an update, but a modern evolution of Java. Interviewers expect candidates to write clean, expressive, and efficient code using new language features.

If you’re preparing for:

• Java Developer
• Backend Engineer
• Spring Boot roles