Core Java Developer Interview Questions for IT Hiring

Introduction

Hiring the right Core Java Developer is critical for IT teams building reliable, high-performance systems. A focused interview process ensures technical fit and long-term maintainability.

This guide provides role-specific Core Java Developer interview questions grouped by basic, intermediate, and advanced levels, plus five pre-screening one-way video interview questions ideal for ScreeningHive.

Core Java Developer Interview Questions

Basic Core Java Developer Interview Questions

• What are the main features of the Java language and platform?
• Explain the difference between JDK, JRE, and JVM.
• What is the difference between an interface and an abstract class in Java?
• How does garbage collection work in Java at a high level?
• Describe the difference between == and equals() when comparing objects.
• What are the core Collection interfaces in Java and when would you use each?
• Explain checked versus unchecked exceptions and when to use each type.
• What are Java 8 lambda expressions and how do they help writing code?

Intermediate Core Java Developer Interview Questions

• Given a multi-threaded application, how would you identify and fix a deadlock? Describe steps and tools you would use.
• How do you choose between ArrayList and LinkedList for a particular use case? Provide an example.
• Explain the differences between synchronized methods and ReentrantLock. When would you prefer one over the other?
• Describe how you would implement a thread-safe cache with expiration in Java. Which data structures and libraries would you use?
• How do Streams and parallel streams differ? Provide a case where parallel streams could harm performance.
• Explain how JDBC connection pooling works and why it is important in enterprise apps.
• Describe an approach to detect and resolve memory leaks in a Java application. Which JVM tools do you use?
• How would you design a RESTful endpoint in Spring Boot that supports pagination, sorting, and filtering? Mention validation and error handling.
• Explain CompletableFuture and demonstrate a scenario where it simplifies asynchronous code.
• Describe unit testing best practices for Java code and which mocking framework you prefer and why.

Advanced Core Java Developer Interview Questions

• How do different Garbage Collector algorithms compare and how would you choose GC settings for a low-latency service?
• Explain class loading in JVM, including parent delegation model and custom class loaders use cases.
• How would you diagnose a production performance problem that appears under peak load? Describe monitoring, profiling, and mitigation steps.
• Design a scalable Java-based microservice architecture for a high-throughput system. Discuss state management, communication patterns, and fault tolerance.
• Explain JVM tuning techniques you have applied to improve throughput or reduce pause times. Provide concrete parameter changes and outcomes.
• Discuss strategies for minimizing object allocation and garbage collection pressure in latency-sensitive code.
• How do you approach safe schema evolution for JPA entities in a microservices environment with backward compatibility concerns?
• Describe how to implement and secure inter-service communication in Java, including authentication, authorization, and transport security.
• Explain approaches to implement event-driven processing in Java, including messaging systems and idempotency considerations.
• As a technical lead, how do you set coding standards, perform architecture reviews, and mentor developers on complex Java topics?

Pre-Screening Video Interview Questions for Core Java Developer

These five one-way video questions are designed for efficient pre-screening on ScreeningHive. Each prompt checks practical skills, communication, and problem-solving suited to early-stage candidate evaluation.

1. Describe a recent Java project you worked on and your specific contributions.

   This evaluates real-world experience, role fit, and ability to communicate technical work succinctly.

2. Explain how you would handle a memory leak in a Java application and name the tools you would use.

   This tests troubleshooting skills and familiarity with JVM tooling such as heap analyzers and profilers.

3. Walk through how you implemented concurrency in a component and how you ensured thread safety.

   This assesses understanding of concurrency primitives, common pitfalls, and practical implementation choices.

4. Provide an example where you optimized Java code for performance and the measurable outcome you achieved.

   This reveals experience with profiling, algorithmic choices, and impact measurement.

5. How do you stay current with Java ecosystem updates and which recent feature have you adopted in your work?

This measures continuous learning, awareness of ecosystem changes, and practical adoption of new Java features.

Conclusion

Using a structured set of Core Java Developer interview questions helps hiring teams assess technical depth, problem solving, and cultural fit. Candidates benefit from clear expectations across skill levels.

ScreeningHive enables faster, standardised hiring through one-way video interviews, reducing screening time and improving consistency. Sign up for a FREE ScreeningHive account to streamline your Java hiring process today.