--- /dev/null
+/*
+ * @(#)LinkedHashMap.java 1.11 03/01/23
+ *
+ * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
+ * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
+ */
+
+package instrumented.java.util;
+/**
+ * <p>Hash table and linked list implementation of the <tt>Map</tt> interface,
+ * with predictable iteration order. This implementation differs from
+ * <tt>HashMap</tt> in that it maintains a doubly-linked list running through
+ * all of its entries. This linked list defines the iteration ordering,
+ * which is normally the order in which keys were inserted into the map
+ * (<i>insertion-order</i>). Note that insertion order is not affected
+ * if a key is <i>re-inserted</i> into the map. (A key <tt>k</tt> is
+ * reinserted into a map <tt>m</tt> if <tt>m.put(k, v)</tt> is invoked when
+ * <tt>m.containsKey(k)</tt> would return <tt>true</tt> immediately prior to
+ * the invocation.)
+ *
+ * <p>This implementation spares its clients from the unspecified, generally
+ * chaotic ordering provided by {@link HashMap} (and {@link Hashtable}),
+ * without incurring the increased cost associated with {@link TreeMap}. It
+ * can be used to produce a copy of a map that has the same order as the
+ * original, regardless of the original map's implementation:
+ * <pre>
+ * void foo(Map m) {
+ * Map copy = new LinkedHashMap(m);
+ * ...
+ * }
+ * </pre>
+ * This technique is particularly useful if a module takes a map on input,
+ * copies it, and later returns results whose order is determined by that of
+ * the copy. (Clients generally appreciate having things returned in the same
+ * order they were presented.)
+ *
+ * <p>A special {@link #LinkedHashMap(int,float,boolean) constructor} is
+ * provided to create a linked hash map whose order of iteration is the order
+ * in which its entries were last accessed, from least-recently accessed to
+ * most-recently (<i>access-order</i>). This kind of map is well-suited to
+ * building LRU caches. Invoking the <tt>put</tt> or <tt>get</tt> method
+ * results in an access to the corresponding entry (assuming it exists after
+ * the invocation completes). The <tt>putAll</tt> method generates one entry
+ * access for each mapping in the specified map, in the order that key-value
+ * mappings are provided by the specified map's entry set iterator. <i>No
+ * other methods generate entry accesses.</i> In particular, operations on
+ * collection-views do <i>not</i> affect the order of iteration of the backing
+ * map.
+ *
+ * <p>The {@link #removeEldestEntry(Map.Entry)} method may be overridden to
+ * impose a policy for removing stale mappings automatically when new mappings
+ * are added to the map.
+ *
+ * <p>This class provides all of the optional <tt>Map</tt> operations, and
+ * permits null elements. Like <tt>HashMap</tt>, it provides constant-time
+ * performance for the basic operations (<tt>add</tt>, <tt>contains</tt> and
+ * <tt>remove</tt>), assuming the the hash function disperses elements
+ * properly among the buckets. Performance is likely to be just slightly
+ * below that of <tt>HashMap</tt>, due to the added expense of maintaining the
+ * linked list, with one exception: Iteration over the collection-views
+ * of a <tt>LinkedHashMap</tt> requires time proportional to the <i>size</i>
+ * of the map, regardless of its capacity. Iteration over a <tt>HashMap</tt>
+ * is likely to be more expensive, requiring time proportional to its
+ * <i>capacity</i>.
+ *
+ * <p>A linked hash map has two parameters that affect its performance:
+ * <i>initial capacity</i> and <i>load factor</i>. They are defined precisely
+ * as for <tt>HashMap</tt>. Note, however, that the penalty for choosing an
+ * excessively high value for initial capacity is less severe for this class
+ * than for <tt>HashMap</tt>, as iteration times for this class are unaffected
+ * by capacity.
+ *
+ * <p><strong>Note that this implementation is not synchronized.</strong> If
+ * multiple threads access a linked hash map concurrently, and at least
+ * one of the threads modifies the map structurally, it <em>must</em> be
+ * synchronized externally. This is typically accomplished by synchronizing
+ * on some object that naturally encapsulates the map. If no such object
+ * exists, the map should be "wrapped" using the
+ * <tt>Collections.synchronizedMap</tt>method. This is best done at creation
+ * time, to prevent accidental unsynchronized access:
+ * <pre>
+ * Map m = Collections.synchronizedMap(new LinkedHashMap(...));
+ * </pre>
+ * A structural modification is any operation that adds or deletes one or more
+ * mappings or, in the case of access-ordered linked hash maps, affects
+ * iteration order. In insertion-ordered linked hash maps, merely changing
+ * the value associated with a key that is already contained in the map is not
+ * a structural modification. <strong>In access-ordered linked hash maps,
+ * merely querying the map with <tt>get</tt> is a structural
+ * modification.</strong>)
+ *
+ * <p>The iterators returned by the <tt>iterator</tt> methods of the
+ * collections returned by all of this class's collection view methods are
+ * <em>fail-fast</em>: if the map is structurally modified at any time after
+ * the iterator is created, in any way except through the iterator's own
+ * remove method, the iterator will throw a
+ * <tt>ConcurrentModificationException</tt>. Thus, in the face of concurrent
+ * modification, the Iterator fails quickly and cleanly, rather than risking
+ * arbitrary, non-deterministic behavior at an undetermined time in the
+ * future.
+ *
+ * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
+ * as it is, generally speaking, impossible to make any hard guarantees in the
+ * presence of unsynchronized concurrent modification. Fail-fast iterators
+ * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
+ * Therefore, it would be wrong to write a program that depended on this
+ * exception for its correctness: <i>the fail-fast behavior of iterators
+ * should be used only to detect bugs.</i>
+ *
+ * <p>This class is a member of the
+ * <a href="{@docRoot}/../guide/collections/index.html">
+ * Java Collections Framework</a>.
+ *
+ * @author Josh Bloch
+ * @version 1.11, 01/23/03
+ * @see Object#hashCode()
+ * @see Collection
+ * @see Map
+ * @see HashMap
+ * @see TreeMap
+ * @see Hashtable
+ * @since JDK1.4
+ */
+
+public class LinkedHashMap extends HashMap {
+ /**
+ * The head of the doubly linked list.
+ */
+ private transient Entry header;
+
+ /**
+ * The iteration ordering method for this linked hash map: <tt>true</tt>
+ * for access-order, <tt>false</tt> for insertion-order.
+ *
+ * @serial
+ */
+ private final boolean accessOrder;
+
+ /**
+ * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance
+ * with the specified initial capacity and load factor.
+ *
+ * @param initialCapacity the initial capacity.
+ * @param loadFactor the load factor.
+ * @throws IllegalArgumentException if the initial capacity is negative
+ * or the load factor is nonpositive.
+ */
+ public LinkedHashMap(int initialCapacity, float loadFactor) {
+ super(initialCapacity, loadFactor);
+ accessOrder = false;
+ }
+
+ /**
+ * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance
+ * with the specified initial capacity and a default load factor (0.75).
+ *
+ * @param initialCapacity the initial capacity.
+ * @throws IllegalArgumentException if the initial capacity is negative.
+ */
+ public LinkedHashMap(int initialCapacity) {
+ super(initialCapacity);
+ accessOrder = false;
+ }
+
+ /**
+ * Constructs an empty insertion-ordered <tt>LinkedHashMap</tt> instance
+ * with a default capacity (16) and load factor (0.75).
+ */
+ public LinkedHashMap() {
+ super();
+ accessOrder = false;
+ }
+
+ /**
+ * Constructs an insertion-ordered <tt>LinkedHashMap</tt> instance with
+ * the same mappings as the specified map. The <tt>LinkedHashMap</tt>
+ * instance is created with a a default load factor (0.75) and an initial
+ * capacity sufficient to hold the mappings in the specified map.
+ *
+ * @param m the map whose mappings are to be placed in this map.
+ * @throws NullPointerException if the specified map is null.
+ */
+ public LinkedHashMap(Map m) {
+ super(m);
+ accessOrder = false;
+ }
+
+ /**
+ * Constructs an empty <tt>LinkedHashMap</tt> instance with the
+ * specified initial capacity, load factor and ordering mode.
+ *
+ * @param initialCapacity the initial capacity.
+ * @param loadFactor the load factor.
+ * @param accessOrder the ordering mode - <tt>true</tt> for
+ * access-order, <tt>false</tt> for insertion-order.
+ * @throws IllegalArgumentException if the initial capacity is negative
+ * or the load factor is nonpositive.
+ */
+ public LinkedHashMap(int initialCapacity, float loadFactor,
+ boolean accessOrder) {
+ super(initialCapacity, loadFactor);
+ this.accessOrder = accessOrder;
+ }
+
+ /**
+ * Called by superclass constructors and pseudoconstructors (clone,
+ * readObject) before any entries are inserted into the map. Initializes
+ * the chain.
+ */
+ void init() {
+ header = new Entry(-1, null, null, null);
+ header.before = header.after = header;
+ }
+
+ /**
+ * Transfer all entries to new table array. This method is called
+ * by superclass resize. It is overridden for performance, as it is
+ * faster to iterate using our linked list.
+ */
+ void transfer(HashMap.Entry[] newTable) {
+ int newCapacity = newTable.length;
+ for (Entry e = header.after; e != header; e = e.after) {
+ int index = indexFor(e.hash, newCapacity);
+ e.next = newTable[index];
+ newTable[index] = e;
+ }
+ }
+
+
+ /**
+ * Returns <tt>true</tt> if this map maps one or more keys to the
+ * specified value.
+ *
+ * @param value value whose presence in this map is to be tested.
+ * @return <tt>true</tt> if this map maps one or more keys to the
+ * specified value.
+ */
+ 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;
+ }
+
+ /**
+ * Returns the value to which this map maps the specified key. Returns
+ * <tt>null</tt> if the map contains no mapping for this key. A return
+ * value of <tt>null</tt> does not <i>necessarily</i> indicate that the
+ * map contains no mapping for the key; it's also possible that the map
+ * explicitly maps the key to <tt>null</tt>. The <tt>containsKey</tt>
+ * operation may be used to distinguish these two cases.
+ *
+ * @return the value to which this map maps the specified key.
+ * @param key key whose associated value is to be returned.
+ */
+ public Object get(Object key) {
+ Entry e = (Entry)getEntry(key);
+ if (e == null)
+ return null;
+ e.recordAccess(this);
+ return e.value;
+ }
+
+ /**
+ * Removes all mappings from this map.
+ */
+ public void clear() {
+ super.clear();
+ header.before = header.after = header;
+ }
+
+ /**
+ * LinkedHashMap entry.
+ */
+ private static class Entry extends HashMap.Entry {
+ // These fields comprise the doubly linked list used for iteration.
+ Entry before, after;
+
+ Entry(int hash, Object key, Object value, HashMap.Entry next) {
+ super(hash, key, value, next);
+ }
+
+ /**
+ * Remove this entry from the linked list.
+ */
+ private void remove() {
+ before.after = after;
+ after.before = before;
+ }
+
+ /**
+ * Insert this entry before the specified existing entry in the list.
+ */
+ private void addBefore(Entry existingEntry) {
+ after = existingEntry;
+ before = existingEntry.before;
+ before.after = this;
+ after.before = this;
+ }
+
+ /**
+ * This method is invoked by the superclass whenever the value
+ * of a pre-existing entry is read by Map.get or modified by Map.set.
+ * If the enclosing Map is access-ordered, it moves the entry
+ * to the end of the list; otherwise, it does nothing.
+ */
+ 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;
+
+ /**
+ * The modCount value that the iterator believes that the backing
+ * List should have. If this expectation is violated, the iterator
+ * has detected concurrent modification.
+ */
+ 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 Object next() { return nextEntry().getKey(); }
+ }
+
+ private class ValueIterator extends LinkedHashIterator {
+ public Object next() { return nextEntry().value; }
+ }
+
+ private class EntryIterator extends LinkedHashIterator {
+ public Object 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(); }
+
+ /**
+ * This override alters behavior of superclass put method. It causes newly
+ * allocated entry to get inserted at the end of the linked list and
+ * removes the eldest entry if appropriate.
+ */
+ void addEntry(int hash, Object key, Object value, int bucketIndex) {
+ createEntry(hash, key, value, bucketIndex);
+
+ // Remove eldest entry if instructed, else grow capacity if appropriate
+ Entry eldest = header.after;
+ if (removeEldestEntry(eldest)) {
+ removeEntryForKey(eldest.key);
+ } else {
+ if (size >= threshold)
+ resize(2 * table.length);
+ }
+ }
+
+ /**
+ * This override differs from addEntry in that it doesn't resize the
+ * table or remove the eldest entry.
+ */
+ void createEntry(int hash, Object key, Object value, int bucketIndex) {
+ Entry e = new Entry(hash, key, value, table[bucketIndex]);
+ table[bucketIndex] = e;
+ e.addBefore(header);
+ size++;
+ }
+
+ /**
+ * Returns <tt>true</tt> if this map should remove its eldest entry.
+ * This method is invoked by <tt>put</tt> and <tt>putAll</tt> after
+ * inserting a new entry into the map. It provides the implementer
+ * with the opportunity to remove the eldest entry each time a new one
+ * is added. This is useful if the map represents a cache: it allows
+ * the map to reduce memory consumption by deleting stale entries.
+ *
+ * <p>Sample use: this override will allow the map to grow up to 100
+ * entries and then delete the eldest entry each time a new entry is
+ * added, maintaining a steady state of 100 entries.
+ * <pre>
+ * private static final int MAX_ENTRIES = 100;
+ *
+ * protected boolean removeEldestEntry(Map.Entry eldest) {
+ * return size() > MAX_ENTRIES;
+ * }
+ * </pre>
+ *
+ * <p>This method typically does not modify the map in any way,
+ * instead allowing the map to modify itself as directed by its
+ * return value. It <i>is</i> permitted for this method to modify
+ * the map directly, but if it does so, it <i>must</i> return
+ * <tt>false</tt> (indicating that the map should not attempt any
+ * further modification). The effects of returning <tt>true</tt>
+ * after modifying the map from within this method are unspecified.
+ *
+ * <p>This implementation merely returns <tt>false</tt> (so that this
+ * map acts like a normal map - the eldest element is never removed).
+ *
+ * @param eldest The least recently inserted entry in the map, or if
+ * this is an access-ordered map, the least recently accessed
+ * entry. This is the entry that will be removed it this
+ * method returns <tt>true</tt>. If the map was empty prior
+ * to the <tt>put</tt> or <tt>putAll</tt> invocation resulting
+ * in this invocation, this will be the entry that was just
+ * inserted; in other words, if the map contains a single
+ * entry, the eldest entry is also the newest.
+ * @return <tt>true</tt> if the eldest entry should be removed
+ * from the map; <tt>false</t> if it should be retained.
+ */
+ protected boolean removeEldestEntry(Map.Entry eldest) {
+ return false;
+ }
+}
projects / Benchmarks_CSolver.git / blobdiff