StackOverflow Fun

Pairing and unicity

public class Pair {
    private String left;
    private String right;
    
    public Pair(String v1, String v2) {
        left = v1;
        right = v2;
    };
    
    public String getLeft() {
        return left;
    };
    
    public String getRight() {
        return right;
    }
    
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((left == null) ? 0 : left.hashCode());
        result = prime * result + ((right == null) ? 0 : right.hashCode());
        return result;
    }
    
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Pair other = (Pair) obj;
        if (left == null) {
            if (other.left != null)
                return false;
        } else if (!left.equals(other.left))
            return false;
        if (right == null) {
            if (other.right != null)
                return false;
        } else if (!right.equals(other.right))
            return false;
        return true;
    }
};

public static void main(String[] args) {

    HashMap<Pair, Integer> myMap = new HashMap<Pair, Integer>();

    List<Pair> list = new ArrayList<Pair>();
    list.add(new Pair("A", "B"));
    list.add(new Pair("A", "B"));
    list.add(new Pair("B", "F"));
    list.add(new Pair("C", "R"));
    list.add(new Pair("A", "R"));
    list.add(new Pair("B", "C"));
    list.add(new Pair("R", "C"));
    list.add(new Pair("R", "C"));

    for (Pair pair : list) {
        if (myMap.containsKey(pair)) {
            myMap.put(pair, myMap.get(pair) + 1);
        } else {
            myMap.put(pair, 1);
        }
    }

    Iterator it = myMap.entrySet().iterator();
    while (it.hasNext()) {
        Map.Entry pairs = (Map.Entry) it.next();
        System.out.println(pairs.getKey() + " = " + pairs.getValue());
        it.remove();
    }
};