Generics in Java

Type parameters make classes and methods work with any type while staying type-safe.

Intermediate

class Box<T> {
    private T value;
    void set(T v) { value = v; }
    T get() { return value; }
}

static <T extends Comparable<T>> T max(T a, T b) {
    return a.compareTo(b) >= 0 ? a : b;
}

Generics catch type errors at compile time. Java implements them by type erasure — the type information is removed at run time, so you can't write new T().

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