HADOOP-13147. Constructors must not call overrideable methods in Pure…

…JavaCrc32C (#6408). Contributed by Sebb.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/PureJavaCrc32C.java

@@ -39,7 +39,7 @@ public class PureJavaCrc32C implements Checksum {
 
   /** Create a new PureJavaCrc32 object. */
   public PureJavaCrc32C() {
-    reset();
+    resetFinal(); // safe to call as it cannot be overridden
   }
 
   @Override
@@ -50,6 +50,12 @@ public long getValue() {
 
   @Override
   public void reset() {
+    resetFinal();
+  }
+
+  // This must be final as it is called by the ctor
+  // (can't also be private, as checkstyle then complains)
+  final void resetFinal() {
     crc = 0xffffffff;
   }
 

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestPureJavaCrc32C.java

@@ -0,0 +1,37 @@
+/**
+ * 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.hadoop.util;
+
+import java.util.zip.Checksum;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+
+public class TestPureJavaCrc32C {
+
+  @Test
+  public void testChecksumInit() {
+    Checksum csum = new PureJavaCrc32C();
+    long crc1 = csum.getValue();
+    csum.reset();
+    long crc2 = csum.getValue();
+    assertEquals("reset should give same as initial value", crc1, crc2);
+  }
+}