What Is the Difference Between Traits in Rust and Interfaces in Java/Go?

Rust traits define shared behavior for types but differ from Java/Go interfaces by allowing default method implementations and supporting associated types. While Java and Go interfaces are purely abstract contracts, Rust traits can provide concrete logic that implementing types inherit or override.

trait Summary {
    fn summarize(&self) -> String;
    fn summary_author(&self) -> String { "Anonymous".to_string() }
}

struct NewsArticle {
    headline: String,
}

impl Summary for NewsArticle {
    fn summarize(&self) -> String {
        format!("Read more: {}", self.headline)
    }
}

Think of a Rust trait as a template that defines what a type can do, similar to an interface in Java or Go. The main difference is that a Rust trait can include actual code (default implementations) that types can use automatically, whereas Java and Go interfaces usually only list method names without code. This makes Rust traits more flexible because they can share logic across types without forcing every type to rewrite the same code.