Generics

Generics provides a way to create classes, interfaces and methods.

Instead of using raw types (eg. Object), you define a placeholder for the type.

public class Box<T> {
    public T item;
    public void setItem(T item) {
        this.item = item;
    }
    public T getitem() {
        return item;
    }
}

import java.net.Inet4Address;  
import java.util.*;  
import java.util.function.Consumer;  

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

public class Main {  
    public static void main(String[] args) {  
        Pair<String, Integer> pair = new OrderedPair<>("hello", 1);  
        System.out.println(pair.getKey());  

    }  
}