SquirrelJME/SquirrelJME

// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// SquirrelJME
//     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
// ---------------------------------------------------------------------------
// SquirrelJME is under the Mozilla Public License Version 2.0.
// See license.mkd for licensing and copyright information.
// ---------------------------------------------------------------------------

package net.multiphasicapps.collections;

import java.util.AbstractSet;
import java.util.Iterator;
import java.util.Set;
import org.jetbrains.annotations.UnmodifiableView;

/**
 * This is a set which cannot be modified.
 *
 * @param <T> The value to store in the set.
 * @since 2016/02/28
 */
@UnmodifiableView
public final class UnmodifiableSet<T>
    extends AbstractSet<T>
{
    /** The set to wrap. */
    protected final Set<T> wrapped;
    
    /**
     * Initializes a set view which cannot be modified.
     *
     * @param __w The set to wrap a view for.
     * @throws NullPointerException On null arguments.
     * @since 2016/02/28
     */
    private UnmodifiableSet(Set<T> __w)
        throws NullPointerException
    {
        // Check
        if (__w == null)
            throw new NullPointerException("NARG");
        
        // Wrap it
        this.wrapped = __w;
    }
    
    /**
     * {@inheritDoc}
     * @since 2016/02/28
     */
    @Override
    public boolean contains(Object __o)
    {
        return this.wrapped.contains(__o);
    }
    
    /**
     * {@inheritDoc}
     * @since 2016/05/12
     */
    @Override
    public boolean isEmpty()
    {
        return this.wrapped.isEmpty();
    }
    
    /**
     * {@inheritDoc}
     * @since 2016/02/28
     */
    @Override
    public Iterator<T> iterator()
    {
        return new Iterator<T>()
            {
                /** The base iterator. */
                final Iterator<T> _base = UnmodifiableSet.this.wrapped.iterator();
                
                /**
                 * {@inheritDoc}
                 * @since 2016/02/28
                 */
                @Override
                public boolean hasNext()
                {
                    return this._base.hasNext();
                }
                
                /**
                 * {@inheritDoc}
                 * @since 2016/02/28
                 */
                @Override
                public T next()
                {
                    return this._base.next();
                }
                
                /**
                 * {@inheritDoc}
                 * @since 2016/02/28
                 */
                @Override
                public void remove()
                {
                    throw new UnsupportedOperationException("RORO");
                }
            };
    }
    
    /**
     * {@inheritDoc}
     * @since 2016/02/28
     */
    @Override
    public int size()
    {
        return this.wrapped.size();
    }
    
    /**
     * This creates a view of the specified set which cannot be modified.
     *
     * @param <T> The type of value the set stores.
     * @param __s The set to wrap to disable modifications of.
     * @return An unmodifiable view of the set.
     * @since 2016/02/28
     */
    public static <T> Set<T> of(Set<T> __s)
    {
        // If already one, return that set
        if (__s instanceof UnmodifiableSet)
            return __s;
        
        // Otherwise create a new one
        return new UnmodifiableSet<T>(__s);
    }
}