What are E, K, N, S, T, U, V in Java Generics

If you are wondering what <E>, <K, V>, <N> and so on are called in Java Generics? Well, they are known as "Type Parameters".

Java Genetics E - K - V - T - U - V Type Parameters

Type Parameters are placeholders for data types that are defined when creating generic classes, interfaces, or methods. They are specified inside angle brackets (<>) when defining a generic class, interface, or method.


    Genetic Interface with Type Parameter E:

    interface Payment<E> {
        void process(E payment);

    Genetic Method with Type Parameter E:

    public <E> void printElement(E element) {

    Genetic Class with Type Parameter E:

    class Container<E> {
        private E item;
        public Container(E item) {
            this.item = item;
        public E getItem() {
            return item;

Naming Conventions of Type Parameters:

    The Type Parameters are represented by single uppercase letters e.g., E, T, K, V.

    Naming ConventionType ParameterUsageExample
    EElementUsed extensively by the Java Collections FrameworkList<E>
    KKeyTypically used in key-value pairs or mapsMap<K, V>
    NNumberOften used for numeric typesList<Number>
    TTypeA general-purpose type parameterBox<T>
    VValueCommonly used in key-value pairs or mapsMap<String, V>
    S, U, V, etc.2nd, 3rd, 4th typesUsed for additional type parametersPair<S, T>, Triple<U, V, W>

This is not an AI-generated article but is demonstrated by a human with Java JDK 21 on a M1 Mac.

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