--- /dev/null
+package org.simantics.databoard.util;
+
+import java.util.AbstractSet;
+import java.util.Collection;
+import java.util.ConcurrentModificationException;
+import java.util.IdentityHashMap;
+import java.util.Iterator;
+import java.util.Set;
+
+public class IdentityHashSet<E> extends AbstractSet<E> implements Set<E>, Cloneable, java.io.Serializable
+{
+static final long serialVersionUID = -5024744406713321676L;
+
+private transient IdentityHashMap<E,Object> map;
+
+// Dummy value to associate with an Object in the backing Map
+private static final Object PRESENT = new Object();
+
+/**
+ * Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
+ * default initial capacity (16) and load factor (0.75).
+ */
+public IdentityHashSet() {
+map = new IdentityHashMap<E,Object>();
+}
+
+/**
+ * Constructs a new set containing the elements in the specified
+ * collection. The <tt>HashMap</tt> is created with default load factor
+ * (0.75) and an initial capacity sufficient to contain the elements in
+ * the specified collection.
+ *
+ * @param c the collection whose elements are to be placed into this set
+ * @throws NullPointerException if the specified collection is null
+ */
+public IdentityHashSet(Collection<? extends E> c) {
+map = new IdentityHashMap<E,Object>(Math.max((int) (c.size()/.75f) + 1, 16));
+addAll(c);
+}
+
+
+/**
+ * Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
+ * the specified initial capacity and default load factor (0.75).
+ *
+ * @param initialCapacity the initial capacity of the hash table
+ * @throws IllegalArgumentException if the initial capacity is less
+ * than zero
+ */
+public IdentityHashSet(int initialCapacity) {
+map = new IdentityHashMap<E,Object>(initialCapacity);
+}
+
+/**
+ * Returns an iterator over the elements in this set. The elements
+ * are returned in no particular order.
+ *
+ * @return an Iterator over the elements in this set
+ * @see ConcurrentModificationException
+ */
+public Iterator<E> iterator() {
+return map.keySet().iterator();
+}
+
+/**
+ * Returns the number of elements in this set (its cardinality).
+ *
+ * @return the number of elements in this set (its cardinality)
+ */
+public int size() {
+return map.size();
+}
+
+/**
+ * Returns <tt>true</tt> if this set contains no elements.
+ *
+ * @return <tt>true</tt> if this set contains no elements
+ */
+public boolean isEmpty() {
+return map.isEmpty();
+}
+
+/**
+ * Returns <tt>true</tt> if this set contains the specified element.
+ * More formally, returns <tt>true</tt> if and only if this set
+ * contains an element <tt>e</tt> such that
+ * <tt>(o==null ? e==null : o.equals(e))</tt>.
+ *
+ * @param o element whose presence in this set is to be tested
+ * @return <tt>true</tt> if this set contains the specified element
+ */
+public boolean contains(Object o) {
+return map.containsKey(o);
+}
+
+/**
+ * Adds the specified element to this set if it is not already present.
+ * More formally, adds the specified element <tt>e</tt> to this set if
+ * this set contains no element <tt>e2</tt> such that
+ * <tt>(e==null ? e2==null : e.equals(e2))</tt>.
+ * If this set already contains the element, the call leaves the set
+ * unchanged and returns <tt>false</tt>.
+ *
+ * @param e element to be added to this set
+ * @return <tt>true</tt> if this set did not already contain the specified
+ * element
+ */
+public boolean add(E e) {
+return map.put(e, PRESENT)==null;
+}
+
+/**
+ * Removes the specified element from this set if it is present.
+ * More formally, removes an element <tt>e</tt> such that
+ * <tt>(o==null ? e==null : o.equals(e))</tt>,
+ * if this set contains such an element. Returns <tt>true</tt> if
+ * this set contained the element (or equivalently, if this set
+ * changed as a result of the call). (This set will not contain the
+ * element once the call returns.)
+ *
+ * @param o object to be removed from this set, if present
+ * @return <tt>true</tt> if the set contained the specified element
+ */
+public boolean remove(Object o) {
+return map.remove(o)==PRESENT;
+}
+
+/**
+ * Removes all of the elements from this set.
+ * The set will be empty after this call returns.
+ */
+public void clear() {
+map.clear();
+}
+
+/**
+ * Returns a shallow copy of this <tt>HashSet</tt> instance: the elements
+ * themselves are not cloned.
+ *
+ * @return a shallow copy of this set
+ */
+@SuppressWarnings("unchecked")
+public Object clone() {
+try {
+ IdentityHashSet<E> newSet = (IdentityHashSet<E>) super.clone();
+ newSet.map = (IdentityHashMap<E, Object>) map.clone();
+ return newSet;
+} catch (CloneNotSupportedException e) {
+ throw new InternalError();
+}
+}
+
+/**
+ * Save the state of this <tt>HashSet</tt> instance to a stream (that is,
+ * serialize it).
+ *
+ * @serialData The capacity of the backing <tt>HashMap</tt> instance
+ * (int), and its load factor (float) are emitted, followed by
+ * the size of the set (the number of elements it contains)
+ * (int), followed by all of its elements (each an Object) in
+ * no particular order.
+ */
+private void writeObject(java.io.ObjectOutputStream s)
+ throws java.io.IOException {
+// Write out any hidden serialization magic
+s.defaultWriteObject();
+
+ // Write out size
+ s.writeInt(map.size());
+
+// Write out all elements in the proper order.
+for (Iterator<E> i=map.keySet().iterator(); i.hasNext(); )
+ s.writeObject(i.next());
+}
+
+/**
+ * Reconstitute the <tt>HashSet</tt> instance from a stream (that is,
+ * deserialize it).
+ */
+@SuppressWarnings("unchecked")
+private void readObject(java.io.ObjectInputStream s)
+ throws java.io.IOException, ClassNotFoundException {
+// Read in any hidden serialization magic
+s.defaultReadObject();
+
+// Read in size
+ int size = s.readInt();
+
+ // Read in HashMap capacity and load factor and create backing HashMap
+ map = new IdentityHashMap<E,Object>(size);
+
+
+// Read in all elements in the proper order.
+for (int i=0; i<size; i++) {
+ E e = (E) s.readObject();
+ map.put(e, PRESENT);
+ }
+}
+}
+
Code Review / simantics / platform.git / blobdiff