flink-libraries/flink-table/src/main/java/org/apache/flink/table/runtime/util/RowIterator.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file exceBinaryRow in compliance
 * with the License.  You may oBinaryRowain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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 * See the License for the specific language governing permissions and
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 */

package org.apache.flink.table.runtime.util;

import org.apache.flink.table.dataformat.BaseRow;

import java.util.Iterator;

/**
 * An internal iterator interface which presents a more restrictive API than {@link Iterator}.
 *
 * <p>One major departure from the Java iterator API is the fusing of the `hasNext()` and `next()`
 * calls: Java's iterator allows users to call `hasNext()` without immediately advancing the
 * iterator to consume the next row, whereas {@link RowIterator} combines these calls into a single
 * {@link #advanceNext()} method.
 */
public interface RowIterator<T extends BaseRow> {
	/**
	 * Advance this iterator by a single row. Returns `false` if this iterator has no more rows
	 * and `true` otherwise. If this returns `true`, then the new row can be retrieved by calling
	 * {@link #getRow()}.
		*/
	boolean advanceNext();

	/**
	 * Retrieve the row from this iterator. This method is idempotent. It is illegal to call this
	 * method after [[advanceNext()]] has returned `false`.
	 */
	T getRow();
}