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Library providing immutable/persistent collection classes for Java. While collections are immutable they provide methods for adding and removing values by creating new modified copies of themselves. Each copy shares almost all of its structure with other copies to minimize memory consumption.

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// Burton Computer Corporation
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package org.javimmutable.collections.inorder;

import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.MapEntry;
import org.javimmutable.collections.SplitableIterator;
import org.javimmutable.collections.array.trie32.TrieArray;
import org.javimmutable.collections.common.AbstractJImmutableMap;
import org.javimmutable.collections.cursors.TransformCursor;
import org.javimmutable.collections.hash.JImmutableHashMap;
import org.javimmutable.collections.iterators.TransformIterator;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;

import static org.javimmutable.collections.common.StreamConstants.SPLITERATOR_ORDERED;

/**
 * JImmutableMap implementation that allows iteration over members in the order in which they
 * were inserted into the map.  Maintains two parallel data structures, one for sorting and
 * the other for storing entries.  Gets are approximately as fast as hash map gets but updates
 * are significantly slower.   Iteration is comparable to sorted map iteration.
 * 

* Use a hash or tree map whenever possible but this class performs well enough for most cases * where insertion order is important to an algorithm. */ @Immutable public class JImmutableInsertOrderMap extends AbstractJImmutableMap { @SuppressWarnings("unchecked") public static final JImmutableInsertOrderMap EMPTY = new JImmutableInsertOrderMap(TrieArray.of(), JImmutableHashMap.of(), 0); private final TrieArray> sortedNodes; private final JImmutableMap> hashedNodes; private final int nextIndex; private JImmutableInsertOrderMap(TrieArray> sortedNodes, JImmutableMap> hashedNodes, int nextIndex) { assert sortedNodes.size() == hashedNodes.size(); this.sortedNodes = sortedNodes; this.hashedNodes = hashedNodes; this.nextIndex = nextIndex; } @SuppressWarnings("unchecked") public static JImmutableInsertOrderMap of() { return (JImmutableInsertOrderMap)EMPTY; } @Override public V getValueOr(K key, V defaultValue) { final Node current = hashedNodes.get(key); return (current != null) ? current.getValue() : defaultValue; } @Nonnull @Override public Holder find(@Nonnull K key) { final Node current = hashedNodes.get(key); return (current != null) ? current : Holders.of(); } @Nonnull @Override public Holder> findEntry(@Nonnull K key) { final Node current = hashedNodes.get(key); return (current != null) ? Holders.of(current) : Holders.of(); } @Nonnull @Override public JImmutableInsertOrderMap assign(@Nonnull K key, V value) { final Node current = hashedNodes.get(key); if (current == null) { final Node newNode = new Node<>(key, value, nextIndex); return new JImmutableInsertOrderMap<>(sortedNodes.assign(newNode.index, newNode), hashedNodes.assign(key, newNode), nextIndex + 1); } else if (current.getValue() == value) { return this; } else { final Node newNode = current.withValue(value); return new JImmutableInsertOrderMap<>(sortedNodes.assign(newNode.index, newNode), hashedNodes.assign(key, newNode), nextIndex); } } @Nonnull @Override public JImmutableInsertOrderMap delete(@Nonnull K key) { final Node current = hashedNodes.get(key); if (current != null) { return new JImmutableInsertOrderMap<>(sortedNodes.delete(current.index), hashedNodes.delete(key), nextIndex); } else { return this; } } @Override public int size() { return hashedNodes.size(); } @Nonnull @Override public JImmutableInsertOrderMap deleteAll() { return of(); } @Override @Nonnull public Cursor> cursor() { return TransformCursor.of(sortedNodes.cursor(), e -> e.getValue()); } @Nonnull @Override public SplitableIterator> iterator() { return TransformIterator.of(sortedNodes.iterator(), e -> e.getValue()); } @Override public int getSpliteratorCharacteristics() { return SPLITERATOR_ORDERED; } @Override public void checkInvariants() { //TODO: fix empty checkInvariants() } /** * An Entry implementation that also stores the sortedKeys index corresponding to this node's key. */ @Immutable private static class Node extends MapEntry implements Holder { private final int index; private Node(K key, V value, int index) { super(key, value); this.index = index; } @Override public boolean isEmpty() { return false; } @Override public boolean isFilled() { return true; } @Override public V getValueOrNull() { return value; } @Override public V getValueOr(V defaultValue) { return value; } private Node withValue(V value) { return new Node<>(key, value, index); } } }





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