Remove HashFunctionIdentity comparators.

The comparators are never used to perform ordering of functions. The
only current use is to determine that two hash functions are
functionally equivalent. A replacement utility class has been added to
test for equality.

src/main/java/org/apache/commons/collections4/bloomfilter/AbstractBloomFilter.java

@@ -212,6 +212,9 @@ public abstract class AbstractBloomFilter implements BloomFilter {
      * @param hasher the Hasher to check
      */
     protected void verifyHasher(final Hasher hasher) {
+        // It is assumed that the filter and hasher have been constructed using the
+        // same hash function. Use the signature for a fast check the hash function is equal.
+        // Collisions will occur at a rate of 1 in 2^64.
         if (shape.getHashFunctionIdentity().getSignature() != hasher.getHashFunctionIdentity().getSignature()) {
             throw new IllegalArgumentException(
                 String.format("Hasher (%s) is not the hasher for shape (%s)",

src/main/java/org/apache/commons/collections4/bloomfilter/hasher/DynamicHasher.java

@@ -177,13 +177,8 @@ public class DynamicHasher implements Hasher {
      */
     @Override
     public PrimitiveIterator.OfInt getBits(final Shape shape) {
-        if (HashFunctionIdentity.COMMON_COMPARATOR.compare(getHashFunctionIdentity(),
+        HashFunctionValidator.checkAreEqual(getHashFunctionIdentity(),
-            shape.getHashFunctionIdentity()) != 0) {
+                                            shape.getHashFunctionIdentity());
-            throw new IllegalArgumentException(
-                String.format("Shape hasher %s is not %s",
-                    HashFunctionIdentity.asCommonString(shape.getHashFunctionIdentity()),
-                    HashFunctionIdentity.asCommonString(getHashFunctionIdentity())));
-        }
         // Use optimised iterator for no values
         return buffers.isEmpty() ? NoValuesIterator.INSTANCE : new Iterator(shape);
     }

src/main/java/org/apache/commons/collections4/bloomfilter/hasher/HashFunctionIdentity.java

@@ -18,7 +18,6 @@
 package org.apache.commons.collections4.bloomfilter.hasher;
 
 import java.nio.charset.StandardCharsets;
-import java.util.Comparator;
 import java.util.Locale;
 
 /**
@@ -63,39 +62,6 @@ public interface HashFunctionIdentity {
         SIGNED, UNSIGNED
     }
 
-    /**
-     * A comparator implementation that performs the most common comparison using the
-     * HashFunctionIdentity name, signedness, and process.
-     */
-    Comparator<HashFunctionIdentity> COMMON_COMPARATOR = new Comparator<HashFunctionIdentity>() {
-        @Override
-        public int compare(final HashFunctionIdentity identity1, final HashFunctionIdentity identity2) {
-            int result = identity1.getName().compareToIgnoreCase(identity2.getName());
-            if (result == 0) {
-                result = identity1.getSignedness().compareTo(identity2.getSignedness());
-            }
-            if (result == 0) {
-                result = identity1.getProcessType().compareTo(identity2.getProcessType());
-            }
-            return result;
-        }
-    };
-
-    /**
-     * A comparator implementation that performs the comparison using all the properties of the
-     * HashFunctionIdentity: name, signedness, process, and provider.
-     */
-    Comparator<HashFunctionIdentity> DEEP_COMPARATOR = new Comparator<HashFunctionIdentity>() {
-        @Override
-        public int compare(final HashFunctionIdentity identity1, final HashFunctionIdentity identity2) {
-            int result = COMMON_COMPARATOR.compare(identity1, identity2);
-            if (result == 0) {
-                result = identity1.getProvider().compareToIgnoreCase(identity2.getProvider());
-            }
-            return result;
-        }
-    };
-
     /**
      * Gets a common formatted string for general display.
      *
@@ -119,10 +85,9 @@ public interface HashFunctionIdentity {
      * @return the signature buffer for the identity
      */
     static byte[] prepareSignatureBuffer(final HashFunctionIdentity identity) {
-
        return String.format("%s-%s-%s",
            identity.getName().toUpperCase(Locale.ROOT), identity.getSignedness(),
-           identity.getProcessType() ).getBytes(StandardCharsets.UTF_8);
+           identity.getProcessType()).getBytes(StandardCharsets.UTF_8);
     }
 
     /**

src/main/java/org/apache/commons/collections4/bloomfilter/hasher/HashFunctionValidator.java

@@ -0,0 +1,61 @@
+/*
+ * 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.commons.collections4.bloomfilter.hasher;
+
+/**
+ * Contains validation for hash functions.
+ */
+final class HashFunctionValidator {
+    /** Do not instantiate. */
+    private HashFunctionValidator() {}
+
+    /**
+     * Compares the identity of the two hash functions. The functions are considered
+     * equal if the signedness, process type and name are equal. The name is not
+     * case specific.
+     *
+     * <p>A pair of functions that are equal would be expected to produce the same
+     * hash output from the same input.
+     *
+     * @param a First hash function.
+     * @param b Second hash function.
+     * @return true, if successful
+     * @see String#equalsIgnoreCase(String)
+     */
+    static boolean areEqual(HashFunctionIdentity a, HashFunctionIdentity b) {
+        return (a.getSignedness() == b.getSignedness() &&
+                a.getProcessType() == b.getProcessType() &&
+                a.getName().equalsIgnoreCase(b.getName()));
+    }
+
+    /**
+     * Compares the identity of the two hash functions and throws an exception if they
+     * are not equal.
+     *
+     * @param a First hash function.
+     * @param b Second hash function.
+     * @see #areEqual(HashFunctionIdentity, HashFunctionIdentity)
+     * @throws IllegalArgumentException if the hash functions are not equal
+     */
+    static void checkAreEqual(HashFunctionIdentity a, HashFunctionIdentity b) {
+        if (!areEqual(a, b)) {
+            throw new IllegalArgumentException(String.format("Hash functions are not equal: (%s) != (%s)",
+                HashFunctionIdentity.asCommonString(a), HashFunctionIdentity.asCommonString(b)));
+        }
+    }
+}

src/main/java/org/apache/commons/collections4/bloomfilter/hasher/Shape.java

@@ -232,7 +232,7 @@ public class Shape {
      * @param numberOfBits the number of bits in the filter.
      * @return the optimal number of hash functions.
      */
-    private int calculateNumberOfHashFunctions(final int numberOfItems, final int numberOfBits) {
+    private static int calculateNumberOfHashFunctions(final int numberOfItems, final int numberOfBits) {
         /*
          * k = round((m / n) * log(2)) We change order so that we use real math rather
          * than integer math.
@@ -258,8 +258,8 @@ public class Shape {
             return
                 other.getNumberOfBits() == getNumberOfBits() &&
                 other.getNumberOfHashFunctions() == getNumberOfHashFunctions() &&
-                HashFunctionIdentity.COMMON_COMPARATOR.compare(getHashFunctionIdentity(),
+                HashFunctionValidator.areEqual(getHashFunctionIdentity(),
-                    other.getHashFunctionIdentity()) == 0;
+                                               other.getHashFunctionIdentity());
         }
         return false;
     }

src/main/java/org/apache/commons/collections4/bloomfilter/hasher/StaticHasher.java

@@ -48,11 +48,8 @@ public final class StaticHasher implements Hasher {
      */
     public StaticHasher(final Hasher hasher, final Shape shape) {
         this(hasher.getBits(shape), shape);
-        if (HashFunctionIdentity.COMMON_COMPARATOR.compare(hasher.getHashFunctionIdentity(),
+        HashFunctionValidator.checkAreEqual(hasher.getHashFunctionIdentity(),
-            shape.getHashFunctionIdentity()) != 0) {
+                                            shape.getHashFunctionIdentity());
-            throw new IllegalArgumentException(String.format("Hasher (%s) is not the same as for shape (%s)",
-                HashFunctionIdentity.asCommonString(hasher.getHashFunctionIdentity()), shape.toString()));
-        }
     }
 
     /**

src/test/java/org/apache/commons/collections4/bloomfilter/hasher/CommonComparatorTest.java

@@ -1,161 +0,0 @@
-/*
-    * 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.commons.collections4.bloomfilter.hasher;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
-
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.TreeSet;
-
-import org.apache.commons.collections4.bloomfilter.hasher.HashFunctionIdentity.ProcessType;
-import org.apache.commons.collections4.bloomfilter.hasher.HashFunctionIdentity.Signedness;
-import org.junit.Test;
-
-/**
- * Tests of the {@link HashFunctionIdentity#COMMON_COMPARATOR}.
- */
-public class CommonComparatorTest {
-
-    private static void assertAfter(final HashFunctionIdentity identity1, final HashFunctionIdentity identity2) {
-        assertTrue(0 < HashFunctionIdentity.COMMON_COMPARATOR.compare(identity1, identity2));
-    }
-
-    private static void assertBefore(final HashFunctionIdentity identity1, final HashFunctionIdentity identity2) {
-        assertTrue(0 > HashFunctionIdentity.COMMON_COMPARATOR.compare(identity1, identity2));
-    }
-
-    /**
-     * Tests the name ordering is not affected by case.
-     */
-    @Test
-    public void nameOrderTestDifferentCapitalization() {
-        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "IMPL1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-
-        assertEquals(0, HashFunctionIdentity.COMMON_COMPARATOR.compare(impl1, impl2));
-    }
-
-    /**
-     * Tests the name ordering.
-     */
-    @Test
-    public void nameOrderTestDifferentNames() {
-        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "impl2", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-
-        assertBefore(impl1, impl2);
-        assertEquals(0, HashFunctionIdentity.COMMON_COMPARATOR.compare(impl1, impl1));
-        assertEquals(0, HashFunctionIdentity.COMMON_COMPARATOR.compare(impl2, impl2));
-        assertAfter(impl2, impl1);
-    }
-
-    /**
-     * Tests that the process type ordering in correct.
-     */
-    @Test
-    public void processTypeOrder() {
-        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.ITERATIVE, 300L);
-
-        assertBefore(impl1, impl2);
-        assertEquals(0, HashFunctionIdentity.COMMON_COMPARATOR.compare(impl1, impl1));
-        assertEquals(0, HashFunctionIdentity.COMMON_COMPARATOR.compare(impl2, impl2));
-        assertAfter(impl2, impl1);
-    }
-
-    /**
-     * Tests that a change in producer does not change the order.
-     */
-    @Test
-    public void producerDoesNotChangeOrder() {
-        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite2", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-
-        assertEquals(0, HashFunctionIdentity.COMMON_COMPARATOR.compare(impl1, impl2));
-    }
-
-    /**
-     * Tests that signedness ordering is correct.
-     */
-    @Test
-    public void signednessOrder() {
-        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.UNSIGNED,
-            ProcessType.CYCLIC, 300L);
-
-        assertBefore(impl1, impl2);
-        assertEquals(0, HashFunctionIdentity.COMMON_COMPARATOR.compare(impl1, impl1));
-        assertEquals(0, HashFunctionIdentity.COMMON_COMPARATOR.compare(impl2, impl2));
-        assertAfter(impl2, impl1);
-    }
-
-    /**
-     * Tests that the ordering is correct when applied ot a collection.
-     */
-    @Test
-    public void testSortOrder() {
-        // in this test the signature is the position in the final collection for the ID
-        final TreeSet<HashFunctionIdentity> result = new TreeSet<>(
-            HashFunctionIdentity.COMMON_COMPARATOR);
-        final List<HashFunctionIdentity> collection = new ArrayList<>();
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED, ProcessType.CYCLIC, 0));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED, ProcessType.ITERATIVE, 1));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.UNSIGNED, ProcessType.CYCLIC, 2));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.UNSIGNED, ProcessType.ITERATIVE, 3));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl2", Signedness.SIGNED, ProcessType.CYCLIC, 4));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl2", Signedness.SIGNED, ProcessType.ITERATIVE, 5));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl2", Signedness.UNSIGNED, ProcessType.CYCLIC, 6));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl2", Signedness.UNSIGNED, ProcessType.ITERATIVE, 7));
-
-        Collections.shuffle(collection);
-
-        result.addAll(collection);
-        long idx = 0;
-        for (final HashFunctionIdentity id : result) {
-            assertEquals("Unexpected order for " + HashFunctionIdentity.asCommonString(id), idx++, id.getSignature());
-        }
-    }
-}

src/test/java/org/apache/commons/collections4/bloomfilter/hasher/DeepComparatorTest.java

@@ -1,188 +0,0 @@
-/*
-    * 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.commons.collections4.bloomfilter.hasher;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
-
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.TreeSet;
-
-import org.apache.commons.collections4.bloomfilter.hasher.HashFunctionIdentity.ProcessType;
-import org.apache.commons.collections4.bloomfilter.hasher.HashFunctionIdentity.Signedness;
-import org.junit.Test;
-
-/**
- * Tests of the {@link HashFunctionIdentity#DEEP_COMPARATOR}.
- */
-public class DeepComparatorTest {
-
-    private static void assertAfter(final HashFunctionIdentity identity1, final HashFunctionIdentity identity2) {
-        assertTrue(0 < HashFunctionIdentity.DEEP_COMPARATOR.compare(identity1, identity2));
-    }
-
-    private static void assertBefore(final HashFunctionIdentity identity1, final HashFunctionIdentity identity2) {
-        assertTrue(0 > HashFunctionIdentity.DEEP_COMPARATOR.compare(identity1, identity2));
-    }
-
-    /**
-     * Tests that name order is not affected by case.
-     */
-    @Test
-    public void nameOrderTestDifferentCapitalization() {
-        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "IMPL1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-
-        assertEquals(0, HashFunctionIdentity.DEEP_COMPARATOR.compare(impl1, impl2));
-    }
-
-    /**
-     * Tests that name order is correct.
-     */
-    @Test
-    public void nameOrderTestDifferentNames() {
-        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "impl2", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-
-        assertBefore(impl1, impl2);
-        assertEquals(0, HashFunctionIdentity.DEEP_COMPARATOR.compare(impl1, impl1));
-        assertEquals(0, HashFunctionIdentity.DEEP_COMPARATOR.compare(impl2, impl2));
-        assertAfter(impl2, impl1);
-    }
-
-    /**
-     * Tests that process type order is correct.
-     */
-    @Test
-    public void processTypeOrder() {
-        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.ITERATIVE, 300L);
-
-        assertBefore(impl1, impl2);
-        assertEquals(0, HashFunctionIdentity.DEEP_COMPARATOR.compare(impl1, impl1));
-        assertEquals(0, HashFunctionIdentity.DEEP_COMPARATOR.compare(impl2, impl2));
-        assertAfter(impl2, impl1);
-    }
-
-    /**
-     * Tests that producer order is correct.
-     */
-    @Test
-    public void producerOrder() {
-        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite2", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-
-        assertBefore(impl1, impl2);
-        assertEquals(0, HashFunctionIdentity.DEEP_COMPARATOR.compare(impl1, impl1));
-        assertEquals(0, HashFunctionIdentity.DEEP_COMPARATOR.compare(impl2, impl2));
-        assertAfter(impl2, impl1);
-    }
-
-    /**
-     * Tests that signedness order is correct.
-     */
-    @Test
-    public void signednessOrder() {
-        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
-            ProcessType.CYCLIC, 300L);
-        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.UNSIGNED,
-            ProcessType.CYCLIC, 300L);
-
-        assertBefore(impl1, impl2);
-        assertEquals(0, HashFunctionIdentity.DEEP_COMPARATOR.compare(impl1, impl1));
-        assertEquals(0, HashFunctionIdentity.DEEP_COMPARATOR.compare(impl2, impl2));
-        assertAfter(impl2, impl1);
-    }
-
-    /**
-     * Tests that the ordering is correct when applied ot a collection.
-     */
-    @Test
-    public void testSortOrder() {
-        // in this test the signature is the position in the final collection for the ID
-        final TreeSet<HashFunctionIdentity> result = new TreeSet<>(HashFunctionIdentity.DEEP_COMPARATOR);
-        final List<HashFunctionIdentity> collection = new ArrayList<>();
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED, ProcessType.CYCLIC, 0));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED, ProcessType.ITERATIVE, 2));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.UNSIGNED, ProcessType.CYCLIC, 4));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.UNSIGNED, ProcessType.ITERATIVE, 6));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl2", Signedness.SIGNED, ProcessType.CYCLIC, 8));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl2", Signedness.SIGNED, ProcessType.ITERATIVE, 10));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite", "impl2", Signedness.UNSIGNED, ProcessType.CYCLIC, 12));
-
-        collection.add(
-            new HashFunctionIdentityImpl("Testing Suite", "impl2", Signedness.UNSIGNED, ProcessType.ITERATIVE, 14));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite2", "impl1", Signedness.SIGNED, ProcessType.CYCLIC, 1));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite2", "impl1", Signedness.SIGNED, ProcessType.ITERATIVE, 3));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite2", "impl1", Signedness.UNSIGNED, ProcessType.CYCLIC, 5));
-
-        collection.add(
-            new HashFunctionIdentityImpl("Testing Suite2", "impl1", Signedness.UNSIGNED, ProcessType.ITERATIVE, 7));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite2", "impl2", Signedness.SIGNED, ProcessType.CYCLIC, 9));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite2", "impl2", Signedness.SIGNED, ProcessType.ITERATIVE, 11));
-
-        collection
-            .add(new HashFunctionIdentityImpl("Testing Suite2", "impl2", Signedness.UNSIGNED, ProcessType.CYCLIC, 13));
-
-        collection.add(
-            new HashFunctionIdentityImpl("Testing Suite2", "impl2", Signedness.UNSIGNED, ProcessType.ITERATIVE, 15));
-
-        Collections.shuffle(collection);
-
-        result.addAll(collection);
-        long idx = 0;
-        for (final HashFunctionIdentity id : result) {
-            assertEquals("Unexpected order for " + id.getProvider() + ":" + HashFunctionIdentity.asCommonString(id),
-                idx++, id.getSignature());
-        }
-    }
-}

src/test/java/org/apache/commons/collections4/bloomfilter/hasher/HashFuctionValidatorTest.java

@@ -0,0 +1,120 @@
+/*
+    * 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.commons.collections4.bloomfilter.hasher;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.apache.commons.collections4.bloomfilter.hasher.HashFunctionIdentity.ProcessType;
+import org.apache.commons.collections4.bloomfilter.hasher.HashFunctionIdentity.Signedness;
+import org.junit.Test;
+
+/**
+ * Tests of the {@link HashFunctionValidator}.
+ */
+public class HashFuctionValidatorTest {
+
+    /**
+     * Tests that name is used in the equality check.
+     */
+    @Test
+    public void testName() {
+        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
+            ProcessType.CYCLIC, 300L);
+        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "impl2", Signedness.SIGNED,
+            ProcessType.CYCLIC, 300L);
+
+        assertTrue(HashFunctionValidator.areEqual(impl1, impl1));
+        assertTrue(HashFunctionValidator.areEqual(impl2, impl2));
+        assertFalse(HashFunctionValidator.areEqual(impl1, impl2));
+        assertFalse(HashFunctionValidator.areEqual(impl2, impl1));
+    }
+
+    /**
+     * Tests that name is not affected by case.
+     */
+    @Test
+    public void testNameIsCaseInsensitive() {
+        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
+            ProcessType.CYCLIC, 300L);
+        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "IMPL1", Signedness.SIGNED,
+            ProcessType.CYCLIC, 300L);
+
+        assertTrue(HashFunctionValidator.areEqual(impl1, impl2));
+    }
+
+    /**
+     * Tests that process type is used in the equality check.
+     */
+    @Test
+    public void testProcessType() {
+        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
+            ProcessType.CYCLIC, 300L);
+        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
+            ProcessType.ITERATIVE, 300L);
+
+        assertTrue(HashFunctionValidator.areEqual(impl1, impl1));
+        assertTrue(HashFunctionValidator.areEqual(impl2, impl2));
+        assertFalse(HashFunctionValidator.areEqual(impl1, impl2));
+        assertFalse(HashFunctionValidator.areEqual(impl2, impl1));
+    }
+
+    /**
+     * Tests that provider is <strong>not</strong> used in the equality check.
+     */
+    @Test
+    public void testProviderIsNotUsedInEqualityCheck() {
+        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
+            ProcessType.CYCLIC, 300L);
+        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite2", "impl1", Signedness.SIGNED,
+            ProcessType.CYCLIC, 300L);
+
+        assertTrue(HashFunctionValidator.areEqual(impl1, impl1));
+        assertTrue(HashFunctionValidator.areEqual(impl2, impl2));
+        assertTrue(HashFunctionValidator.areEqual(impl1, impl2));
+        assertTrue(HashFunctionValidator.areEqual(impl2, impl1));
+    }
+
+    /**
+     * Tests that signedness is used in the equality check.
+     */
+    @Test
+    public void testSignedness() {
+        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
+            ProcessType.CYCLIC, 300L);
+        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.UNSIGNED,
+            ProcessType.CYCLIC, 300L);
+
+        assertTrue(HashFunctionValidator.areEqual(impl1, impl1));
+        assertTrue(HashFunctionValidator.areEqual(impl2, impl2));
+        assertFalse(HashFunctionValidator.areEqual(impl1, impl2));
+        assertFalse(HashFunctionValidator.areEqual(impl2, impl1));
+    }
+
+    /**
+     * Test the check method throws when the two hash functions are not equal.
+     */
+    @Test(expected=IllegalArgumentException.class)
+    public void testCheckThrows() {
+        final HashFunctionIdentityImpl impl1 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.SIGNED,
+            ProcessType.CYCLIC, 300L);
+        final HashFunctionIdentityImpl impl2 = new HashFunctionIdentityImpl("Testing Suite", "impl1", Signedness.UNSIGNED,
+            ProcessType.CYCLIC, 300L);
+        HashFunctionValidator.checkAreEqual(impl1, impl2);
+    }
+}

src/test/java/org/apache/commons/collections4/bloomfilter/hasher/StaticHasherTest.java

@@ -187,7 +187,11 @@ public class StaticHasherTest {
 
         assertEquals(5, hasher.size());
         assertEquals(shape, hasher.getShape());
-        assertEquals(0, HashFunctionIdentity.DEEP_COMPARATOR.compare(testFunction, hasher.getHashFunctionIdentity()));
+        // All function properties are equal
+        assertEquals(testFunction.getName(), hasher.getHashFunctionIdentity().getName());
+        assertEquals(testFunction.getProcessType(), hasher.getHashFunctionIdentity().getProcessType());
+        assertEquals(testFunction.getProvider(), hasher.getHashFunctionIdentity().getProvider());
+        assertEquals(testFunction.getSignedness(), hasher.getHashFunctionIdentity().getSignedness());
 
         iter = hasher.getBits(shape);
         int idx = 0;