Java DeveloperInterview Questions & Answers
Prepare for your placement drives and technical screenings with these core questions and answers tailored for junior Java Developer candidates.
Q1:What is the difference between an Abstract Class and an Interface in Java?
Answer: An Interface defines a contract (behavior) and supports multiple inheritance, with all methods being implicitly public abstract (before Java 8). An Abstract Class can store instance variables, declare constructor methods, and define non-abstract methods with implementation details, but a class can inherit only one abstract class.
Q2:How does the Java Garbage Collector work?
Answer: The Java Garbage Collector automatically manages memory by identifying and deleting unreferenced objects in the heap. It uses a generational hypothesis, dividing the heap into Young Generation (where new objects reside) and Old Generation (for long-lived objects), scanning them periodically to free memory without manual developer intervention.
Q3:What are Java Streams and how do they differ from Collections?
Answer: Collections are data structures that store elements in memory. Streams are wrappers around collections or data sources that let you process elements declaratively using functional-style operations (filter, map, reduce). Streams do not store data, do not modify the original collection, and support lazy execution.
How to Answer Behavioral Interview Questions
When answering situational questions (like “tell me about a time you resolved a conflict”), always use the STAR method:
- Situation: Set the context and describe the background.
- Task: Explain the core challenge or goal you had to address.
- Action: Detail the specific steps you took to resolve it.
- Result: Highlight the positive outcome and what you learned.
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