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Ripple dataflow utilities

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package net.fortytwo.flow;

import java.util.Collection;

/**
 * A helper class for collectors
 *
 * @author Joshua Shinavier (http://fortytwo.net)
 */
abstract class SimpleReadOnlyCollection implements Collection
{
    public boolean isEmpty()
    {
        return 0 == size();
    }

    public boolean contains(final Object o)
    {
        for (T t : this)
        {
            if (o.equals(t))
            {
                return true;
            }
        }

        return false;
    }

    public T[] toArray()
    {
        T[] array = (T[]) new Object[size()];

        int i = 0;
        for (T t : this)
        {
            array[i] = t;
            i++;
        }

        return array;
    }

    // FIXME: I'm unsure whether I've implemented this superfluous method correctly.
    public  U[] toArray(U[] array)
    {
        int size = size();
        U[] targetArray = (size <= array.length)
                ? array
                : (U[]) new Object[size];

        int i = 0;
        for (T t : this)
        {
            targetArray[i] = (U) t;
            i++;
        }

        if (size < targetArray.length)
        {
            targetArray[size] = null;
        }

        return targetArray;
    }

    public boolean add(final T t) {
        throw new UnsupportedOperationException();
    }

    public boolean remove(final Object o) {
        throw new UnsupportedOperationException();
    }

    public boolean containsAll(final Collection objects)
    {
        for (Object o : objects) {
            if (contains(o))
            {
                return true;
            }
        }

        return false;
    }

    public boolean addAll(final Collection ts) {
        throw new UnsupportedOperationException();
    }

    public boolean removeAll(final Collection objects) {
        throw new UnsupportedOperationException();
    }

    public boolean retainAll(final Collection objects) {
        throw new UnsupportedOperationException();
    }

    public void clear() {
        throw new UnsupportedOperationException();
    }
}