Aad

package CCM.fifoMap;
import java.util.*;

/**
 *
 * @author  Philippe Fery
 * @version 1.0
 */
public class FIFOMap {
    private HashMap map;
    private ArrayList order;
    
    public FIFOMap() {
        map = new  HashMap();
        order = new ArrayList();
    }
    
    public void put(Object key, Object value){
        if(!map.containsKey(key)){
            System.out.println("New pair K-V");
            order.add(key);
        }else{
            System.out.println("K exists, V modified, insertion at end of queue");
            order.add(order.remove(order.indexOf(key)));
        }
        map.put(key, value);
    }
    
    public Object pop(){
        Object o = null;
        if(order.size()>0){
            Object key = order.remove(0);
            o = map.remove(key);
            System.out.println("Removing last object: Key="+key+" Value="+o);
        }else{
            System.out.println("The map is empty: can't remove any object!");
        }
        return o;
    }
    
    public Object get(Object key){
        Object value = null;
        if(order.contains(key)){
            value = map.get(key);
        }
        System.out.println("You get " + value + " with key " + key.toString());
        return value;
    }
    
    public Object get(int index){
        Object o = null;
        if(order.size()>index){
            Object key = order.get(index);
            o = map.get(key);
            System.out.println("Index exists: getting index <"+index+"> and returning "+o.toString());
        }else{
            System.out.println("Index <"+index+"> doesn't exist: returning NULL");
        }
        return o;
    }
}

package CCM.fifoMap;

/**
 *
 * @author  Philippe FERY
 * @version 1.0
 */
public class FIFOMapTester {

    public FIFOMapTester() {
    }

    public static void main (String args[]) {
        FIFOMap map = new FIFOMap();
        map.put("A","Alex");
        map.put("P","Phil");
        map.get("A");
        map.put("G","Gérald");
        map.put("L","Laurent S");
        
        map.put("L","Laurent VDB");
        
        map.pop();
        map.get(0);
        map.get(1);
        map.get(2);
        map.get(3);
        map.get(4);
        map.get(5);
    }
}