HashMap and Set Performance Optimization in Android Kotlin

Using List.contains() instead of Set.contains() in your Android app? You might be making it 900x slower than it needs to be.

Tung Doan breaks down HashMap and Set performance optimization in Android Kotlin with real benchmarks, memory comparisons, and production-ready code examples. This comprehensive guide shows exactly when to use HashMap vs ArrayMap, HashSet vs List, and how to avoid common pitfalls that kill app performance.

Key Takeaways

• HashSet lookups are 900x faster than List.contains() for 10,000 items
• ArrayMap uses 8x less memory than HashMap but slower for datasets over 1,000 items
• Pre-sizing collections eliminates costly resize operations during growth
• Poor hash functions degrade HashMap from O(1) to O(n) performance
• Multi-level indexing in RecyclerView adapters eliminates O(n) searches

The article includes a complete production-ready shopping cart ViewModel implementation and a multi-level product filter system that handles thousands of items efficiently.