[HUDI-1075] Implement simple clustering strategies to create ClusteringPlan and to run the plan

hudi-client/hudi-client-common/src/test/java/org/apache/hudi/utils/TestConcatenatingIterator.java

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+/*
+ * 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.hudi.utils;
+
+import org.apache.hudi.client.utils.ConcatenatingIterator;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.fail;
+
+public class TestConcatenatingIterator {
+
+  // Simple test for iterator concatenation
+  @Test
+  public void testConcatBasic() {
+    Iterator<Integer> i1 = Arrays.asList(5, 3, 2, 1).iterator();
+    Iterator<Integer> i2 = new ArrayList<Integer>().iterator(); // empty iterator
+    Iterator<Integer> i3 = Arrays.asList(3).iterator();
+
+    ConcatenatingIterator<Integer> ci = new ConcatenatingIterator<>(Arrays.asList(i1, i2, i3));
+    List<Integer> allElements = new ArrayList<>();
+    while (ci.hasNext()) {
+      allElements.add(ci.next());
+    }
+
+    assertEquals(5, allElements.size());
+    assertEquals(Arrays.asList(5, 3, 2, 1, 3), allElements);
+  }
+
+  @Test
+  public void testConcatError() {
+    Iterator<Integer> i1 = new ArrayList<Integer>().iterator(); // empty iterator
+
+    ConcatenatingIterator<Integer> ci = new ConcatenatingIterator<>(Arrays.asList(i1));
+    assertFalse(ci.hasNext());
+    try {
+      ci.next();
+      fail("expected error for empty iterator");
+    } catch (IllegalArgumentException e) {
+      //
+    }
+  }
+}