[FLINK-11461] [test] Remove the useless MockRecordReader class

This closes #7610.

flink-runtime/src/test/java/org/apache/flink/runtime/operators/sort/MockRecordReader.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 except in compliance
- * with the License.  You may obtain 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,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-
-package org.apache.flink.runtime.operators.sort;
-
-import java.util.concurrent.ArrayBlockingQueue;
-import java.util.concurrent.BlockingQueue;
-
-import org.apache.flink.types.Record;
-import org.apache.flink.util.MutableObjectIterator;
-
-/**
- */
-public class MockRecordReader implements MutableObjectIterator<Record> {
-	private final Record SENTINEL = new Record();
-
-	private final BlockingQueue<Record> queue;
-
-	public MockRecordReader() {
-		this.queue = new ArrayBlockingQueue<Record>(32, false);
-	}
-
-	public MockRecordReader(int size) {
-		this.queue = new ArrayBlockingQueue<Record>(size, false);
-	}
-
-	@Override
-	public Record next(Record reuse) {
-		Record r = null;
-		while (r == null) {
-			try {
-				r = queue.take();
-			} catch (InterruptedException iex) {
-				throw new RuntimeException("Reader was interrupted.");
-			}
-		}
-
-		if (r == SENTINEL) {
-			// put the sentinel back, to ensure that repeated calls do not block
-			try {
-				queue.put(r);
-			} catch (InterruptedException e) {
-				throw new RuntimeException("Reader was interrupted.");
-			}
-			return null;
-		} else {
-			r.copyTo(reuse);
-			return reuse;
-		}
-	}
-
-	@Override
-	public Record next() {
-		Record r = null;
-		while (r == null) {
-			try {
-				r = queue.take();
-			} catch (InterruptedException iex) {
-				throw new RuntimeException("Reader was interrupted.");
-			}
-		}
-
-		if (r == SENTINEL) {
-			// put the sentinel back, to ensure that repeated calls do not block
-			try {
-				queue.put(r);
-			} catch (InterruptedException e) {
-				throw new RuntimeException("Reader was interrupted.");
-			}
-			return null;
-		} else {
-			Record result = new Record(r.getNumFields());
-			r.copyTo(result);
-			return result;
-		}
-	}
-
-	public void emit(Record element) throws InterruptedException {
-		queue.put(element.createCopy());
-	}
-
-	public void close() {
-		try {
-			queue.put(SENTINEL);
-		} catch (InterruptedException e) {
-			throw new RuntimeException(e);
-		}
-	}
-}