Java Generics

Generics occured in https://www.hackerrank.com/challenges/30-generics/problem this challenge, so that I quickly want to remember that. Generic Types Generics allow to use and write parametrized types. A generic class is defined like this:

class name<T1, T2, …, Tn> { /* … */ }

A type variable can be any non-primitive type you specify: any class type, any interface type, any array type, or even another type variable.

public interface Pair<K, V> {
    public K getKey();
    public V getValue();
}

Generic Methods

Method declarations can also be generic.

3: public static void sink(T t) { } 4: public static T identity(T t) { return t; } 5: public static T noGood(T t) { return t; } // DOES NOT COMPILE

References [1] https://docs.oracle.com/javase/tutorial/java/generics/types.html [2] https://docs.oracle.com/javase/tutorial/extra/generics/methods.html