Writing Generic Functions

This lesson covers writing a generic function in Java, so you can build a flexible method that works across multiple types. It's for anyone searching "Java generics usage."

Generics (<T>) let you write a method that works with "any type at all," without pinning it down to one. Handy when you want to reuse the same logic for both numbers and strings.

The example's definition, static <T extends Comparable<T>> T larger(T a, T b), lets the same method compare both numbers with larger(3, 7) and strings with larger("apple", "banana"). The constraint T extends Comparable<T> limits it to types that can actually be compared.

A common early mistake is not seeing the point of the type constraint. An unconstrained T alone doesn't guarantee comparison operators work, and adding a constraint like Comparable improves safety.

In real projects, generics are widely used to boost code reuse, saving you from writing nearly-identical methods for every type over and over.

📖 Reference code

public class Main {
    static <T extends Comparable<T>> T larger(T a, T b) {
        return a.compareTo(b) > 0 ? a : b;
    }

    public static void main(String[] args) {
        System.out.println(larger(3, 7));
        System.out.println(larger("apple", "banana"));
    }
}

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🧪 This site can't compile or run Java directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).