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modules/collections/src/main/java/net/multiphasicapps/collections/UnmodifiableIterator.java

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// -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
// ---------------------------------------------------------------------------
// SquirrelJME
//     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
// ---------------------------------------------------------------------------
// SquirrelJME is under the GNU General Public License v3+, or later.
// See license.mkd for licensing and copyright information.
// ---------------------------------------------------------------------------

package net.multiphasicapps.collections;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * This creates an unmodifiable iterator over an existing iterator.
 *
 * @param <T> The type to use.
 * @since 2018/05/13
 */
public final class UnmodifiableIterator<T>
    implements Iterator<T>
{
    /** The source iterator. */
    protected final Iterator<T> source;
    
    /**
     * Initializes the iterator.
     *
     * @param __it The source iterator.
     * @throws NullPointerException On null arguments.
     * @since 2018/05/13
     */
    UnmodifiableIterator(Iterator<T> __it)
        throws NullPointerException
    {
        if (__it == null)
            throw new NullPointerException("NARG");
        
        this.source = __it;
    }
    
    /**
     * {@inheritDoc}
     * @since 2108/05/13
     */
    @Override
    public final boolean hasNext()
    {
        return this.source.hasNext();
    }
    
    /**
     * {@inheritDoc}
     * @since 2108/05/13
     */
    @Override
    public final T next()
        throws NoSuchElementException
    {
        return this.source.next();
    }
    
    /**
     * {@inheritDoc}
     * @throws UnsupportedOperationException Always.
     * @since 2108/05/13
     */
    @Override
    public final void remove()
        throws UnsupportedOperationException
    {
        throw new UnsupportedOperationException("RORO");
    }
    
    /**
     * Wraps the given iterable.
     *
     * @param <T> The iterator type.
     * @param __i The iterable to wrap.
     * @return The wrapped iterator.
     * @throws NullPointerException On null arguments.
     * @since 2018/05/13
     */
    public static <T> Iterator<T> of(Iterable<T> __i)
        throws NullPointerException
    {
        if (__i == null)
            throw new NullPointerException("NARG");
        
        return new UnmodifiableIterator<T>(__i.iterator());
    }
    
    /**
     * Wraps the given iterator.
     *
     * @param <T> The iterator type.
     * @param __i The iterator to wrap.
     * @return The wrapped iterator.
     * @throws NullPointerException On null arguments.
     * @since 2018/05/13
     */
    public static <T> Iterator<T> of(Iterator<T> __i)
        throws NullPointerException
    {
        if (__i == null)
            throw new NullPointerException("NARG");
        
        return new UnmodifiableIterator<T>(__i);
    }
    
    /**
     * Wraps the given array.
     *
     * @param <T> The iterator type.
     * @param __a The array to wrap.
     * @return The iterator for the array.
     * @throws NullPointerException On null arguments.
     * @since 2018/05/13
     */
    @SuppressWarnings({"unchecked"})
    public static <T> Iterator<T> of(T... __a)
        throws NullPointerException
    {
        if (__a == null)
            throw new NullPointerException("NARG");
        
        return new UnmodifiableArrayIterator<T>(__a, 0, __a.length);
    }
    
    /**
     * Wraps the given array.
     *
     * @param <T> The iterator type.
     * @param __a The input array.
     * @param __o The offset into the array.
     * @param __l The number of elements to read.
     * @throws ArrayIndexOutOfBoundsException If the offset and/or length are
     * negative or exceed the array bounds.
     * @return The iterator for the array.
     * @throws NullPointerException On null arguments.
     * @since 2018/05/13
     */
    public static <T> Iterator<T> of(T[] __a, int __o, int __l)
        throws ArrayIndexOutOfBoundsException, NullPointerException
    {
        if (__a == null)
            throw new NullPointerException("NARG");
        if (__o < 0 || __l < 0 || (__o + __l) > __a.length)
            throw new ArrayIndexOutOfBoundsException("IOOB");
        
        return new UnmodifiableArrayIterator<T>(__a, __o, __l);
    }
}