ChunkedRecordStream.java

package nl.helixsoft.recordstream;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import nl.helixsoft.util.ObjectUtils;

/**
 * A chunked record stream groups subsequent records that share the value for one
 * field, the key.
 * All consecutive records that have the same value in the key column
 * are accumulated in a List, one list for each value.
 */
public class ChunkedRecordStream extends AbstractStream<List<Record>> implements NextUntilNull<List<Record>> 
{
	private final RecordStream parent;
	private final String key;
	private Record next;
	
	public ChunkedRecordStream (String key, RecordStream parent) throws StreamException
	{
		this.parent = parent;
		next = parent.getNext();
		this.key = key;
	}
	
	public List<Record> getNext() throws StreamException
	{
		if (next == null) return null; // eof.
		Object currentKey = next.get(key);
		List<Record> result = new ArrayList<Record>();
		
		do
		{
			result.add(next);
			next = parent.getNext();
			if (next == null) break;
		} 
		while (next != null && ObjectUtils.safeEquals(currentKey, next.get(key)));
		return result;
	}

	@Override
	public Iterator<List<Record>> iterator() 
	{
		return new IteratorHelper<List<Record>>(this);
	}

}