Map m1 = new HashMap();
    m1.put("map", "HashMap");
    m1.put("schildt", "java2");
    m1.put("mathew", "Hyden");
    m1.put("schildt", "java2s");
    print(m1.keySet()); 
    print(m1.values()); 

    SortedMap sm = new TreeMap();
    sm.put("map", "TreeMap");
    sm.put("schildt", "java2");
    sm.put("mathew", "Hyden");
    sm.put("schildt", "java2s");
    print(sm.keySet()); 
    print(sm.values());

    LinkedHashMap lm = new LinkedHashMap();
    lm .put("map", "LinkedHashMap");
    lm .put("schildt", "java2");
    lm .put("mathew", "Hyden");
    lm .put("schildt", "java2s");
    print(lm .keySet()); 
    print(lm .values()); 

What is the difference between these three? I don't see any difference in the output as all the three has keySet and values. What are Hashtables?