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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
// http://www.burton-computer.com
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// Copyright (c) 2018, Burton Computer Corporation
// All rights reserved.
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package org.javimmutable.collections.array;

import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.Indexed;
import org.javimmutable.collections.JImmutableArray;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.SplitableIterator;
import org.javimmutable.collections.common.AbstractJImmutableArray;
import org.javimmutable.collections.common.MutableDelta;
import org.javimmutable.collections.iterators.IteratorHelper;
import org.javimmutable.collections.iterators.TransformIterator;
import org.javimmutable.collections.serialization.JImmutableArrayProxy;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;
import java.io.Serializable;
import java.util.Iterator;
import java.util.stream.Collector;

@Immutable
public class JImmutableTrieArray
    extends AbstractJImmutableArray
    implements Serializable
{
    @SuppressWarnings("unchecked")
    private static final JImmutableTrieArray EMPTY = new JImmutableTrieArray(TrieNode.of(), 0);
    private static final long serialVersionUID = -121805;

    private final TrieNode root;
    private final int size;

    private JImmutableTrieArray(TrieNode root,
                                int size)
    {
        this.root = root;
        this.size = size;
    }

    public static  Builder builder()
    {
        return new Builder<>();
    }

    @Nonnull
    public static  Collector> collector()
    {
        return Collector., JImmutableArray>of(() -> new Builder<>(),
                                                               (b, v) -> b.add(v),
                                                               (b1, b2) -> (Builder)b1.add(b2.iterator()),
                                                               b -> b.build());
    }

    @SuppressWarnings("unchecked")
    public static  JImmutableTrieArray of()
    {
        return EMPTY;
    }

    /**
     * Efficiently constructs a TrieArray containing the objects from source (in the specified range).
     * In the constructed TrieArray objects will have array indexes starting at 0 (i.e. indexes
     * from the source are not carried over) so if offset is 10 then source.get(10) will map to
     * array.get(0).
     *
     * @deprecated use builder() instead
     */
    @Deprecated
    public static  JImmutableArray of(Indexed source,
                                            int offset,
                                            int limit)
    {
        return JImmutableTrieArray.builder().add(source, offset, limit).build();
    }

    @Override
    @Nullable
    public T getValueOr(int index,
                        @Nullable T defaultValue)
    {
        if (root.getShift() < TrieNode.shiftForIndex(index)) {
            return defaultValue;
        } else {
            return root.getValueOr(root.getShift(), index, defaultValue);
        }
    }

    @Nonnull
    @Override
    public Holder find(int index)
    {
        if (root.getShift() < TrieNode.shiftForIndex(index)) {
            return Holders.of();
        } else {
            return root.find(root.getShift(), index);
        }
    }

    @Nonnull
    @Override
    public JImmutableTrieArray assign(int index,
                                         @Nullable T value)
    {
        MutableDelta sizeDelta = new MutableDelta();
        TrieNode newRoot = root.paddedToMinimumDepthForShift(TrieNode.shiftForIndex(index));
        newRoot = newRoot.assign(newRoot.getShift(), index, value, sizeDelta);
        return (newRoot == root) ? this : new JImmutableTrieArray<>(newRoot, size + sizeDelta.getValue());
    }

    @Nonnull
    @Override
    public JImmutableTrieArray delete(int index)
    {
        if (root.getShift() < TrieNode.shiftForIndex(index)) {
            return this;
        } else {
            MutableDelta sizeDelta = new MutableDelta();
            final TrieNode newRoot = root.delete(root.getShift(), index, sizeDelta).trimmedToMinimumDepth();
            return (newRoot == root) ? this : new JImmutableTrieArray<>(newRoot, size + sizeDelta.getValue());
        }
    }

    @Override
    public int size()
    {
        return size;
    }

    @Nonnull
    @Override
    public JImmutableTrieArray deleteAll()
    {
        return of();
    }

    @Override
    @Nonnull
    public Cursor> cursor()
    {
        return root.cursor();
    }

    @Nonnull
    @Override
    public SplitableIterator> iterator()
    {
        return root.iterator();
    }

    @Override
    public void checkInvariants()
    {
        root.checkInvariants();
    }

    @Override
    public boolean equals(Object o)
    {
        return (o == this) || ((o instanceof JImmutableArray) && IteratorHelper.iteratorEquals(iterator(), ((JImmutableArray)o).iterator()));
    }

    @Override
    public int hashCode()
    {
        return IteratorHelper.iteratorHashCode(iterator());
    }

    @Override
    public String toString()
    {
        return IteratorHelper.iteratorToString(iterator());
    }

    private Object writeReplace()
    {
        return new JImmutableArrayProxy(this);
    }

    public static class Builder
        implements JImmutableArray.Builder
    {
        private final TrieArrayBuilder builder;

        private Builder()
        {
            builder = new TrieArrayBuilder<>();
        }

        @Override
        public int size()
        {
            return builder.size();
        }

        @Nonnull
        @Override
        public Builder add(T value)
        {
            builder.add(value);
            return this;
        }

        @Nonnull
        @Override
        public JImmutableTrieArray build()
        {
            return builder.size() == 0 ? of() : new JImmutableTrieArray<>(builder.build(), builder.size());
        }

        @Nonnull
        private Iterator iterator()
        {
            return TransformIterator.of(builder.build().iterator(), e -> e.getValue());
        }
    }
}




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