Practice Exercises
Test your understanding of hash tables with these interactive exercises.
Practice Exercises
Score: 0 / 0
What is the bucket index for key "elderberry" in a HashMap with capacity 8?
hashCode("elderberry") = 683702092
Quick Reference
Formulas
bucketIndex = hashCode % capacity
loadFactor = size / capacity
threshold = capacity × 0.75
rehash when: size > threshold
Key Concepts
- Collision: Two keys with the same bucket index
- Chaining: Store colliding entries in a linked list
- Load Factor: How full the table is (default 0.75)
- Rehashing: Doubling capacity when threshold exceeded
Common Mistakes to Avoid
Forgetting modulo
Always use hashCode % capacity to get the index
Confusing size and capacity
Size = number of entries. Capacity = array length
Threshold calculation
Threshold = capacity × loadFactor (floor the result)
New indices after rehash
Use the NEW capacity in the modulo: hashCode % newCapacity