vigna/fastutil

Health v2 · maintenance only

Flags: no_releases

Adoption not part of the score

2230 stars · 230 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

fastutil is a Java library that extends the Java Collections Framework with type-specific maps, sets, lists, and queues for primitives and references, offering small memory footprint and fast access. It also provides 64-bit big arrays and fast binary/text I/O classes.

Use cases

• store large collections of primitive ints without boxing overhead
• reduce memory footprint of maps and sets in a Java application
• use 64-bit indexed big arrays larger than 2^31 elements
• read and write binary files quickly in Java
• replace HashMap with a faster primitive-keyed map
• sort primitive arrays efficiently

When to choose

• your Java code is bottlenecked by autoboxing or standard collection memory overhead
• you need collections keyed or valued by primitives with standard Map/Set interfaces
• you need big arrays exceeding integer index limits

When to avoid

• your collections are small and performance is not critical
• you want a minimal dependency footprint without using the core jar or a minimized jar
• you are not on the JVM

Facets

library · maturity stable

serialization file-system developer-tools developer-tools performance jvm primitive-collections java-collections memory-efficiency big-arrays sorting-algorithms algorithms

Member repositories

For agents

markdown · JSON · MCP: product_card(name="vigna/fastutil")