public class LinkedHashMap<K,V>
 extends HashMap<K,V>
 implements Map<K,V>
{
 ...
}

private static class Entry<K,V> extends HashMap.Entry<K,V> {
 // These fields comprise the doubly linked list used for iteration.
 Entry<K,V> before, after;
Entry(int hash, K key, V value, HashMap.Entry<K,V> next) {
  super(hash, key, value, next);
 }
 ...
}

public static void main(String[] args)
{
 LinkedHashMap<String, String> linkedHashMap =
   new LinkedHashMap<String, String>();
 linkedHashMap.put("111", "111");
 linkedHashMap.put("222", "222");
}

public LinkedHashMap() {
 super();
  accessOrder = false;
 }

 public HashMap() {
 this.loadFactor = DEFAULT_LOAD_FACTOR;
  threshold = (int)(DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
  table = new Entry[DEFAULT_INITIAL_CAPACITY];
  init();
 }

void init() {
 header = new Entry<K,V>(-1, null, null, null);
 header.before = header.after = header;
}

/**
 * The head of the doubly linked list.
 */
private transient Entry<K,V> header;

public V put(K key, V value) {
 if (key == null)
  return putForNullKey(value);
 int hash = hash(key.hashCode());
 int i = indexFor(hash, table.length);
 for (Entry<K,V> e = table[i]; e != null; e = e.next) {
  Object k;
  if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
   V oldValue = e.value;
   e.value = value;
   e.recordAccess(this);
   return oldValue;
  }
 }
 modCount++;
 addEntry(hash, key, value, i);
 return null;
}

void addEntry(int hash, K key, V value, int bucketIndex) {
 createEntry(hash, key, value, bucketIndex);

 // Remove eldest entry if instructed, else grow capacity if appropriate
 Entry<K,V> eldest = header.after;
 if (removeEldestEntry(eldest)) {
  removeEntryForKey(eldest.key);
 } else {
  if (size >= threshold)
   resize(2 * table.length);
 }
}

void createEntry(int hash, K key, V value, int bucketIndex) {
 HashMap.Entry<K,V> old = table[bucketIndex];
 Entry<K,V> e = new Entry<K,V>(hash, key, value, old);
 table[bucketIndex] = e;
 e.addBefore(header);
 size++;
}

private void addBefore(Entry<K,V> existingEntry) {
 after = existingEntry;
 before = existingEntry.before;
 before.after = this;
 after.before = this;
}

public class LRUCache extends LinkedHashMap
{
 public LRUCache(int maxSize)
 {
  super(maxSize, 0.75F, true);
  maxElements = maxSize;
 }

 protected boolean removeEldestEntry(java.util.Map.Entry eldest)
 {
  return size() > maxElements;
 }
 private static final long serialVersionUID = 1L;
 protected int maxElements;
}

public LinkedHashMap(int initialCapacity,
   float loadFactor,
      boolean accessOrder) {
 super(initialCapacity, loadFactor);
 this.accessOrder = accessOrder;
}

public V get(Object key) {
 Entry<K,V> e = (Entry<K,V>)getEntry(key);
 if (e == null)
  return null;
 e.recordAccess(this);
 return e.value;
}

public V put(K key, V value) {
 if (key == null)
  return putForNullKey(value);
 int hash = hash(key.hashCode());
 int i = indexFor(hash, table.length);
 for (Entry<K,V> e = table[i]; e != null; e = e.next) {
  Object k;
  if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
   V oldValue = e.value;
   e.value = value;
   e.recordAccess(this);
   return oldValue;
  }
 }
 modCount++;
 addEntry(hash, key, value, i);
 return null;
}

void recordAccess(HashMap<K,V> m) {
 LinkedHashMap<K,V> lm = (LinkedHashMap<K,V>)m;
 if (lm.accessOrder) {
  lm.modCount++;
  remove();
  addBefore(lm.header);
 }
}

private void remove() {
 before.after = after;
 after.before = before;
}

private void addBefore(Entry<K,V> existingEntry) {
 after = existingEntry;
 before = existingEntry.before;
 before.after = this;
 after.before = this;
}

public static void main(String[] args)
{
 LinkedHashMap<String, String> linkedHashMap =
   new LinkedHashMap<String, String>(16, 0.75f, true);
 linkedHashMap.put("111", "111");
 linkedHashMap.put("222", "222");
 linkedHashMap.put("333", "333");
 linkedHashMap.put("444", "444");
 loopLinkedHashMap(linkedHashMap);
 linkedHashMap.get("111");
 loopLinkedHashMap(linkedHashMap);
 linkedHashMap.put("222", "2222");
 loopLinkedHashMap(linkedHashMap);
}
 
public static void loopLinkedHashMap(LinkedHashMap<String, String> linkedHashMap)
{
 Set<Map.Entry<String, String>> set = inkedHashMap.entrySet();
 Iterator<Map.Entry<String, String>> iterator = set.iterator();
 
 while (iterator.hasNext())
 {
  System.out.print(iterator.next() + "\t");
 }
 System.out.println();
}

111=111 222=222 333=333 444=444 
222=222 333=333 444=444 111=111 
333=333 444=444 111=111 222=2222