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Java Fundamentals Practice (Interactive)

Intuition

Learning through practice: Practice problems are like training drills — they help you apply knowledge and identify areas that need more study.

Why it matters: Regular practice builds confidence and reveals patterns in how concepts are tested. Each problem reinforces key programming concepts.

The key insight: Making mistakes during practice is valuable — each error points to a concept that needs clarification.

Java — Fundamentals Practice

10 auto-graded practice problems covering Java fundamentals. Select an answer, submit, and review the explanation.

Types and Variables

Access Modifiers

Collections

Streams

Concurrency

Generics

Garbage Collection

JIT Optimization (Hard)

Class Loading Order (Hard)

Cross-References

Common Mistakes

Forgetting that b + 1 promotes to int: Byte arithmetic automatically widens to int. Assigning back to byte requires an explicit cast. Use b += 1 for implicit casting.

Confusing volatile with synchronization: volatile ensures visibility but not atomicity. count++ is not atomic even with volatile. Use synchronized or AtomicInteger for compound operations.

Using == to compare strings: == compares object identity, not content. Use .equals() or .compareTo() for string comparison.