Bug 202254 Exception is thrown when category values are null and type of X axis is set to DateTime
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/computation/DataSetIterator.java
/***********************************************************************
 * Copyright (c) 2004 Actuate Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http:www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * Actuate Corporation - initial API and implementation
 ***********************************************************************/
package org.eclipse.birt.chart.computation;
import java.text.MessageFormat;
import java.util.Collection;
import java.util.Iterator;
import org.eclipse.birt.chart.engine.i18n.Messages;
import org.eclipse.birt.chart.exception.ChartException;
import org.eclipse.birt.chart.model.data.DataSet;
import org.eclipse.birt.chart.model.data.DateTimeDataSet;
import org.eclipse.birt.chart.model.data.NumberDataSet;
import org.eclipse.birt.chart.model.data.TextDataSet;
import org.eclipse.birt.chart.plugin.ChartEnginePlugin;
import org.eclipse.birt.chart.util.CDateTime;
import com.ibm.icu.util.Calendar;
/**
 * An immutable class with convenience methods provided to retrieve data from
 * the dataset
 */
public final class DataSetIterator implements Iterator