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Java Lookahead Parser Generator. Generator produces LALR(k) parsers. Grammar rules are entered using annotations. Rule annotation can be attached to reducer method, which keeps rule and it's action together.

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/*
 * Copyright (C) 2012 Timo Vesalainen
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.vesalainen.parser.util;

import java.util.Iterator;

/**
 *
 * @author tkv
 */
public class PeekableIterator implements Iterator
{
    private Iterator iterator;
    private T peek;

    public PeekableIterator(Iterator iterator)
    {
        this.iterator = iterator;
    }

    public boolean hasNext()
    {
        return peek != null || iterator.hasNext();
    }

    public boolean hasNextNext()
    {
        if (peek == null)
        {
            peek();
        }
        return iterator.hasNext();
    }

    public T next()
    {
        if (peek == null)
        {
            return iterator.next();
        }
        else
        {
            T p = peek;
            peek = null;
            return p;
        }
    }

    public T peek()
    {
        if (peek == null)
        {
            if (iterator.hasNext())
            {
                peek = iterator.next();
            }
            else
            {
                return null;
            }
        }
        return peek;
    }

    public void remove()
    {
        throw new UnsupportedOperationException("Not supported yet.");
    }
}