Mid-level Java Developer interview questions

Shared by steffi mueller

Cards 52

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Last updated Jun 2, 2026

[Core Java] Explain the Java Memory Model.

Defines how threads interact through memory, visibility, ordering guarantees.

[Multithreading] What is the difference between synchronized and ReentrantLock?

ReentrantLock more flexible: fairness, tryLock, multiple conditions.

[Collections] How does HashMap work internally?

Array of buckets, hashing, linked lists or trees for collisions (Java 8+).

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