/*
 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 * 
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 * 
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 * 
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 * 
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */
package org.graalvm.visualvm.heapviewer.utils;

import java.util.Iterator;

/**
 *
 * @author Jiri Sedlacek
 */
public abstract class ExcludingIterator<T> implements Iterator<T> {
    
    private final Iterator<T> iterator;
    private T next;

    
    protected ExcludingIterator(Iterator<T> iterator) {
        this.iterator = iterator;
        computeNext();
    }
    
    
    protected abstract boolean exclude(T item);
    

    @Override
    public boolean hasNext() {
        return next != null;
    }

    @Override
    public T next() {
        T ret = next;
        computeNext();
        return ret;
    }

    private void computeNext() {
        while (iterator.hasNext()) {
            next = iterator.next();
            if (!exclude(next)) return;
        }
        next = null;
    }
    
}
