// every Java class implicitly inherits from Object 
// common methods: toString(), equals(..), hashCode(), ...

public class Pair<E> {

    private E v1, v2;
    
    // * Java provides a default constructor, if there is NO constructor
    public Pair() {
                
    }
    
    public Pair(E v1, E v2) {
        this.v1 = v1;
        this.v2 = v2;
    }
    
    @Override
    // format: Pair@xyzxyz [ 'E', 'T' ]
    public String toString() {
        //return super.toString() + " [ " + v1 + ", " + v2 + " ]"; // string concatenation
        return String.format("%s [ %s, %s ]", super.toString(), v1, v2);
    }
    
    
    public static void main(String[] args) {
        Pair<String> p1 = new Pair<>();
        
        Pair<Character> p2 = new Pair<>('E', 'T');    // auto boxing
        
        Pair<Character> p3 = p2;   // p3 is an alias (nick-name) of p2
        
        System.out.println(p1.toString()); 
        System.out.println(p2.toString());
        System.out.println(p3.toString());
    }
    
}