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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.indexed;

import org.javimmutable.collections.Indexed;

import javax.annotation.concurrent.Immutable;

/**
 * Indexed implementation backed by a java array.
 */
@Immutable
public class IndexedArray
    implements Indexed
{
    private final T[] values;

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

    /**
     * Produces an instance using the provided array.  This makes the instance unsafe for sharing since
     * changes to the array 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  IndexedArray retained(T[] values)
    {
        return new IndexedArray(values);
    }

    private IndexedArray(T[] values)
    {
        this.values = values;
    }

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

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