Java Generics Multiple Type Parameters Example

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Java Generics Tutorial

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A generic class can have multiple type parameters. In this article, we will learn how to create a generic class and interface with multiple type parameters examples.

Java Generics Multiple Type Parameters Example

Let's create an OrderedPair class which is a generic multiple type parameters class. The generic OrderedPair class, which implements the generic Pair interface:

public class GenericMultipleTypeParametersExample {
 public static void main(String[] args) {
  OrderedPair<String, Integer> p1 = new OrderedPair<>("Even", 8);
  System.out.println(p1.getKey());
  System.out.println(p1.getValue());
  
  OrderedPair<String, String>  p2 = new OrderedPair<>("hello", "world");
  System.out.println(p2.getKey());
  System.out.println(p2.getValue());
  
  OrderedPair<String, Employee>  p3 = new OrderedPair<>("key", new Employee("Ramesh"));
  System.out.println(p3.getKey());
  System.out.println(p3.getValue().getName());
 }
}

class Employee{
 private String name;
 Employee(String name){
  this.name = name;
 }
 
 public String getName(){
  return this.name;
 }
}

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

class OrderedPair<K, V> implements Pair<K, V> {

    private K key;
    private V value;

    public OrderedPair(K key, V value) {
 this.key = key;
 this.value = value;
    }

    public K getKey() { return key; }
    public V getValue() { return value; }
}

Output:

Even
8
hello
world
key
Ramesh

Real-world Example for Multiple Type Parameters

HashMap class is a good example of Multiple Type Parameters.

public class HashMap<K,V> extends AbstractMap<K,V>
    implements Map<K,V>, Cloneable, Serializable {
//...
}

The interface type Map interface is a good example for Multiple Type Parameters.

public interface Map<K, V> {
...
}

Related Java Generics Examples

Java Generics Upper Bounded Wildcards Example
Java Generics Lower Bounded Wildcards Example
Java Generic Methods Examples
Java Generic Interface Examples
Java Generic Class Examples
Java Generics Multiple Type Parameters Example

Java Generics Wildcards Example

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