jdk1.7之LinkedHashMap

package org.springframework.beans;


import java.util.ConcurrentModificationException;
import java.util.HashMap;
import java.util.Iterator;


import java.util.Map;


public class LinkedHashMap extends HashMap implements Map {


private static final long serialVersionUID = 3801124242820219131L;


private transient Entry header;


private final boolean accessOrder;


public LinkedHashMap(int initialCapacity, float loadFactor) {
super(initialCapacity, loadFactor);
accessOrder = false;
}


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


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


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


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


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


@Override
void transfer(HashMap.Entry[] newTable, boolean rehash) {
int newCapacity = newTable.length;
for (Entry e = header.after; e != header; e = e.after) {
if (rehash)
e.hash = (e.key == null) ? 0 : hash(e.key);
int index = indexFor(e.hash, newCapacity);
e.next = newTable[index];
newTable[index] = e;
}
}


public boolean containsValue(Object value) {
// Overridden to take advantage of faster iterator
if (value == null) {
for (Entry e = header.after; e != header; e = e.after)
if (e.value == null)
return true;
} else {
for (Entry e = header.after; e != header; e = e.after)
if (value.equals(e.value))
return true;
}
return false;
}


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


public void clear() {
super.clear();
header.before = header.after = header;
}


private static class Entry extends HashMap.Entry {
// These fields comprise the doubly linked list used for iteration.
Entry before, after;


Entry(int hash, K key, V value, HashMap.Entry next) {
super(hash, key, value, next);
}


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


private void addBefore(Entry existingEntry) {
after = existingEntry;
before = existingEntry.before;
before.after = this;
after.before = this;
}


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


void recordRemoval(HashMap m) {
remove();
}
}


private abstract class LinkedHashIterator implements Iterator {
Entry nextEntry = header.after;
Entry lastReturned = null;


int expectedModCount = modCount;


public boolean hasNext() {
return nextEntry != header;
}


public void remove() {
if (lastReturned == null)
throw new IllegalStateException();
if (modCount != expectedModCount)
throw new ConcurrentModificationException();


LinkedHashMap.this.remove(lastReturned.key);
lastReturned = null;
expectedModCount = modCount;
}


Entry nextEntry() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
if (nextEntry == header)
throw new NoSuchElementException();


Entry e = lastReturned = nextEntry;
nextEntry = e.after;
return e;
}
}


private class KeyIterator extends LinkedHashIterator {
public K next() {
return nextEntry().getKey();
}
}


private class ValueIterator extends LinkedHashIterator {
public V next() {
return nextEntry().value;
}
}


private class EntryIterator extends LinkedHashIterator> {
public Map.Entry next() {
return nextEntry();
}
}


// These Overrides alter the behavior of superclass view iterator() methods
Iterator newKeyIterator() {
return new KeyIterator();
}


Iterator newValueIterator() {
return new ValueIterator();
}


Iterator> newEntryIterator() {
return new EntryIterator();
}


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


// Remove eldest entry if instructed
Entry eldest = header.after;
if (removeEldestEntry(eldest)) {
removeEntryForKey(eldest.key);
}
}


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


protected boolean removeEldestEntry(Map.Entry eldest) {
return false;
}
}