RandomSubList.java

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package ca.uqac.lif.synthia.random;
 
import ca.uqac.lif.synthia.Picker;
import ca.uqac.lif.synthia.Shrinkable;
import ca.uqac.lif.synthia.string.RandomSubString;
import ca.uqac.lif.synthia.util.NothingPicker;
 
import java.util.ArrayList;
import java.util.List;
 
/**
 * An equivalent of {@link RandomSubString} but for lists.
 *
 * @param <T> The type of the list used by the {@link Picker}.
 * @ingroup API
 */
public class RandomSubList<T> implements Shrinkable<List<T>>
{
 
    /**
     * {@link RandomBoolean} used to determine if a element of the list will be added in the sublist
     * or not.
     */
    protected RandomBoolean m_pick;
 
    /**
     * If the element will be added in the sublist, this {@link RandomBoolean} is used to determine if
     * the element will be added as is or be first passed to the {@link Shrinkable}
     * {@link #m_listReducer}.
     */
    protected RandomBoolean m_asIs;
 
    /**
     * {@link Shrinkable} to reduce elements when {@link #m_asIs} decides that the curent element
     * will be reduced. If it's the case, this picker uses the  {@link #shrink(List)} method,
     * passes the element as parameter and uses the {@link Picker#pick()} method of the created
     * picker to generated the element to add in the sublist.
     */
    protected Shrinkable<T> m_listReducer;
 
    /**
     * The list of elements used to generate sublists.
     */
    protected List<T> m_elements;
 
    /**
     * Private constructor used in the {@link #duplicate(boolean)} method.
     *
     * @param pick         The {@link #m_pick} attribute.
     * @param as_is        The {@link #m_asIs} attribute.
     * @param elements     The {@link #m_elements} attribute.
     * @param list_reducer The {@link #m_listReducer} attribute.
     */
    private RandomSubList(RandomBoolean pick, RandomBoolean as_is, List<T> elements,
            Shrinkable<T> list_reducer)
    {
        m_pick = pick;
        m_asIs = as_is;
        m_elements = elements;
        m_listReducer = list_reducer;
    }
 
    /**
     * Public method to create a new instance of the class.
     *
     * @param elements     The list of elements used to generate sublists.
     * @param list_reducer The {@link Shrinkable} used to reduce elements of the original list.
     */
    public RandomSubList(List<T> elements, Shrinkable<T> list_reducer)
    {
        m_pick = new RandomBoolean();
        m_asIs = new RandomBoolean();
        m_elements = elements;
        m_listReducer = list_reducer;
    }
 
    @Override
    public void reset()
    {
        m_pick.reset();
        m_asIs.reset();
        m_listReducer.reset();
    }
 
    @Override
    public List<T> pick()
    {
        List<T> output_list = new ArrayList<>();
        for (T m_element : m_elements)
        {
            if (m_pick.pick())
            {
                if (m_asIs.pick())
                {
                    output_list.add(m_element);
                }
                else
                {
                    output_list.add(m_listReducer.shrink(m_element, new RandomFloat(), 1).pick());
                }
            }
        }
 
        return output_list;
    }
 
    @Override
    public Picker<List<T>> duplicate(boolean with_state)
    {
        return new RandomSubList<T>(m_pick.duplicate(with_state), m_asIs.duplicate(with_state),
                new ArrayList<T>(m_elements), (Shrinkable<T>) m_listReducer.duplicate(with_state));
 
    }
 
    /**
     * Create a new {@link RandomSubList} picker based on a given list. If this list is
     * empty, the method will return a {@link NothingPicker}. The new instance will also have the same
     * internal states for the {@link #m_listReducer}, {@link #m_pick} and {@link #m_asIs} attributes
     * as the original one.
     *
     * @param element The list used by the new {@link RandomSubList} picker to produce sublists.
     * @return The new instance of the class or a {@link NothingPicker}.
     * @warning Depending of the content of the list, it is possible that the returned object is a
     * {@link NothingPicker}. If a {@link RandomSubList} is returned, it is also possible that some of
     * the sublists generated by the {@link #pick()} method of this instance could generate
     * {@link ca.uqac.lif.synthia.NoMoreElementException}'s.
     */
    @Override 
    public Shrinkable<List<T>> shrink(List<T> element, Picker<Float> decision, float magnitude)
    {
        if (!element.getClass().getSimpleName().equals("ArrayList"))
        {
            return new NothingPicker<List<T>>();
        }
        else
        {
            List<T> objects = (List<T>) element;
 
            if (objects.isEmpty())
            {
                return new NothingPicker<List<T>>();
            }
 
            return new RandomSubList<T>(m_pick, m_asIs.duplicate(true), objects,
                    (Shrinkable<T>) m_listReducer.duplicate(true));
        }
    }
 
    @Override
    public Shrinkable<List<T>> shrink(List<T> o)
    {
        return shrink(o, RandomFloat.instance, 1);
    }
}