How do generics in Rust differ from those in Java?

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How do generics in Rust differ from those in Java?

Asked on Dec 20, 2025

Answer

Generics in Rust and Java both allow for type parameterization, but they differ significantly in implementation and behavior. Rust uses monomorphization to generate concrete types at compile time, ensuring zero-cost abstractions, while Java uses type erasure, which removes generic type information at runtime.

Example Concept: In Rust, generics are implemented through monomorphization, where the compiler generates specific versions of functions and structs for each concrete type used, leading to optimized performance. In contrast, Java uses type erasure, meaning generic type information is removed at runtime, and all generic types are treated as Object, which can lead to type safety issues and requires explicit casting.

Additional Comment:

Rust's approach ensures that there is no runtime overhead for using generics, as all type checks are done at compile time.
Java's type erasure allows for backward compatibility with older versions of the language but can result in less type safety.
Rust's generics can be constrained with traits, providing more flexibility and control over what types can be used.
Java uses bounded type parameters to restrict the types that can be used with generics.

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