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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) 2021, Burton Computer Corporation
// All rights reserved.
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package org.javimmutable.collections.indexed;

import org.javimmutable.collections.Indexed;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

@Immutable
public class IndexedList
    implements Indexed,
               Iterable
{
    private final List values;

    private IndexedList(List values)
    {
        this.values = values;
    }

    /**
     * Produces an instance using a copy of the specified List to ensure that changes to the List
     * will not influence the values returned by the instance's methods.  This is generally preferred
     * to the unsafe() constructor.
     */
    public static  IndexedList copied(List values)
    {
        return new IndexedList(new ArrayList(values));
    }

    /**
     * Produces an instance using the provided List.  This makes the instance unsafe for sharing since
     * changes to the List will cause changes to this instance's values.  However this can be useful
     * when performance is important and the instance will not be shared or retained beyond a single
     * method scope.
     */
    public static  IndexedList retained(List values)
    {
        return new IndexedList(values);
    }

    @Override
    public T get(int index)
    {
        return values.get(index);
    }

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

    @Override
    @Nonnull
    public Iterator iterator()
    {
        final Iterator i = values.iterator();
        return new Iterator()
        {
            @Override
            public boolean hasNext()
            {
                return i.hasNext();
            }

            @Override
            public T next()
            {
                return i.next();
            }
        };
    }
}