put IndexFilter in separate file.

put BitMapTracker and ArrayTracker back as enclosed classes in
IndexFilter

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

@@ -1,51 +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;
-
-import java.util.function.IntPredicate;
-
-/**
- * An IndexTracker implementation that uses an array of integers to track whether or not a
- * number has been seen.  Suitable for Shapes that have few hash functions.
- * @since 4.5
- */
-public class ArrayTracker implements IntPredicate {
-    private int[] seen;
-    private int populated;
-
-    /**
-     * Constructs the tracker based on the shape.
-     * @param shape the shape to build the tracker for.
-     */
-    ArrayTracker(Shape shape) {
-        seen = new int[shape.getNumberOfHashFunctions()];
-    }
-
-    @Override
-    public boolean test(int number) {
-        if (number < 0) {
-            throw new IndexOutOfBoundsException("number may not be less than zero. " + number);
-        }
-        for (int i = 0; i < populated; i++) {
-            if (seen[i] == number) {
-                return false;
-            }
-        }
-        seen[populated++] = number;
-        return true;
-    }
-}

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

@@ -1,43 +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;
-
-import java.util.function.IntPredicate;
-
-/**
- * An IndexTracker implementation that uses an array of bit maps to track whether or not a
- * number has been seen.
- * @since 4.5
- */
-public class BitMapTracker implements IntPredicate {
-    private long[] bits;
-
-    /**
-     * Constructs a bit map based tracker for the specified shape.
-     * @param shape The shape that is being generated.
-     */
-    BitMapTracker(Shape shape) {
-        bits = new long[BitMap.numberOfBitMaps(shape.getNumberOfBits())];
-    }
-
-    @Override
-    public boolean test(int number) {
-        boolean retval = !BitMap.contains(bits, number);
-        BitMap.set(bits, number);
-        return retval;
-    }
-}

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

@@ -55,63 +55,4 @@ public interface Hasher {
      * @return the iterator of integers
      */
     IndexProducer uniqueIndices(Shape shape);
-
-    /**
-     * A convenience class for Hasher implementations to filter out duplicate indices.
-     *
-     * <p><em>If the index is negative the behavior is not defined.</em></p>
-     *
-     * <p>This is conceptually a unique filter implemented as a {@code IntPredicate}.</p>
-     * @since 4.5
-     */
-    final class IndexFilter implements IntPredicate {
-        private final IntPredicate tracker;
-        private final int size;
-        private final IntPredicate consumer;
-
-        /**
-         * Creates an instance optimized for the specified shape.
-         * @param shape The shape that is being generated.
-         * @param consumer The consumer to accept the values.
-         * @return an IndexFilter optimized for the specified shape.
-         */
-        public static IndexFilter create(Shape shape, IntPredicate consumer) {
-            return new IndexFilter(shape, consumer);
-        }
-
-        /**
-         * Creates an instance optimized for the specified shape.
-         * @param shape The shape that is being generated.
-         * @param consumer The consumer to accept the values.
-         */
-        private IndexFilter(Shape shape, IntPredicate consumer) {
-            this.size = shape.getNumberOfBits();
-            this.consumer = consumer;
-            if (BitMap.numberOfBitMaps(shape.getNumberOfBits()) * Long.BYTES < (long) shape.getNumberOfHashFunctions()
-                    * Integer.BYTES) {
-                this.tracker = new BitMapTracker(shape);
-            } else {
-                this.tracker = new ArrayTracker(shape);
-            }
-        }
-
-        /**
-         * Test if the number should be processed by the {@code consumer}.
-         *
-         * <p>If the number has <em>not</em> been seen before it is passed to the {@code consumer} and the result returned.
-         * If the number has been seen before the {@code consumer} is not called and {@code true} returned.</p>
-         *
-         * <p><em>If the input is not in the range [0,size) an IndexOutOfBoundsException exception is thrown.</em></p>
-         *
-         * @param number the number to check.
-         * @return {@code true} if processing should continue, {@code false} otherwise.
-         */
-        @Override
-        public boolean test(int number) {
-            if (number >= size) {
-                throw new IndexOutOfBoundsException(String.format("number too large %d >= %d", number, size));
-            }
-            return tracker.test(number) ? consumer.test(number) : true;
-        }
-    }
 }

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

@@ -0,0 +1,118 @@
+package org.apache.commons.collections4.bloomfilter;
+
+import java.util.function.IntPredicate;
+
+/**
+ * A convenience class for Hasher implementations to filter out duplicate indices.
+ *
+ * <p><em>If the index is negative the behavior is not defined.</em></p>
+ *
+ * <p>This is conceptually a unique filter implemented as a {@code IntPredicate}.</p>
+ * @since 4.5
+ */
+public final class IndexFilter implements IntPredicate {
+    private final IntPredicate tracker;
+    private final int size;
+    private final IntPredicate consumer;
+
+    /**
+     * Creates an instance optimized for the specified shape.
+     * @param shape The shape that is being generated.
+     * @param consumer The consumer to accept the values.
+     * @return an IndexFilter optimized for the specified shape.
+     */
+    public static IndexFilter create(Shape shape, IntPredicate consumer) {
+        return new IndexFilter(shape, consumer);
+    }
+
+    /**
+     * Creates an instance optimized for the specified shape.
+     * @param shape The shape that is being generated.
+     * @param consumer The consumer to accept the values.
+     */
+    private IndexFilter(Shape shape, IntPredicate consumer) {
+        this.size = shape.getNumberOfBits();
+        this.consumer = consumer;
+        if (BitMap.numberOfBitMaps(shape.getNumberOfBits()) * Long.BYTES < (long) shape.getNumberOfHashFunctions()
+                * Integer.BYTES) {
+            this.tracker = new BitMapTracker(shape);
+        } else {
+            this.tracker = new ArrayTracker(shape);
+        }
+    }
+
+    /**
+     * Test if the number should be processed by the {@code consumer}.
+     *
+     * <p>If the number has <em>not</em> been seen before it is passed to the {@code consumer} and the result returned.
+     * If the number has been seen before the {@code consumer} is not called and {@code true} returned.</p>
+     *
+     * <p><em>If the input is not in the range [0,size) an IndexOutOfBoundsException exception is thrown.</em></p>
+     *
+     * @param number the number to check.
+     * @return {@code true} if processing should continue, {@code false} otherwise.
+     */
+    @Override
+    public boolean test(int number) {
+        if (number >= size) {
+            throw new IndexOutOfBoundsException(String.format("number too large %d >= %d", number, size));
+        }
+        return tracker.test(number) ? consumer.test(number) : true;
+    }
+
+    /**
+     * An IndexTracker implementation that uses an array of integers to track whether or not a
+     * number has been seen.  Suitable for Shapes that have few hash functions.
+     * @since 4.5
+     */
+    static class ArrayTracker implements IntPredicate {
+        private int[] seen;
+        private int populated;
+
+        /**
+         * Constructs the tracker based on the shape.
+         * @param shape the shape to build the tracker for.
+         */
+        ArrayTracker(Shape shape) {
+            seen = new int[shape.getNumberOfHashFunctions()];
+        }
+
+        @Override
+        public boolean test(int number) {
+            if (number < 0) {
+                throw new IndexOutOfBoundsException("number may not be less than zero. " + number);
+            }
+            for (int i = 0; i < populated; i++) {
+                if (seen[i] == number) {
+                    return false;
+                }
+            }
+            seen[populated++] = number;
+            return true;
+        }
+    }
+
+    /**
+     * An IndexTracker implementation that uses an array of bit maps to track whether or not a
+     * number has been seen.
+     * @since 4.5
+     */
+    static class BitMapTracker implements IntPredicate {
+        private long[] bits;
+
+        /**
+         * Constructs a bit map based tracker for the specified shape.
+         * @param shape The shape that is being generated.
+         */
+        BitMapTracker(Shape shape) {
+            bits = new long[BitMap.numberOfBitMaps(shape.getNumberOfBits())];
+        }
+
+        @Override
+        public boolean test(int number) {
+            boolean retval = !BitMap.contains(bits, number);
+            BitMap.set(bits, number);
+            return retval;
+        }
+    }
+}

src/test/java/org/apache/commons/collections4/bloomfilter/ArrayTrackerTest.java

@@ -32,7 +32,7 @@ public class ArrayTrackerTest {
     @Test
     public void testSeen() {
         Shape shape = Shape.fromKM(3, 12);
-        IntPredicate tracker = new ArrayTracker(shape);
+        IntPredicate tracker = new IndexFilter.ArrayTracker(shape);
 
         assertTrue(tracker.test(0));
         assertFalse(tracker.test(0));

src/test/java/org/apache/commons/collections4/bloomfilter/BitMapTrackerTest.java

@@ -31,7 +31,7 @@ public class BitMapTrackerTest {
     @Test
     public void testSeen() {
         Shape shape = Shape.fromKM(3, 12);
-        IntPredicate tracker = new BitMapTracker(shape);
+        IntPredicate tracker = new IndexFilter.BitMapTracker(shape);
 
         assertTrue(tracker.test(0));
         assertFalse(tracker.test(0));

src/test/java/org/apache/commons/collections4/bloomfilter/IndexFilterTest.java

@@ -28,7 +28,9 @@ import java.util.List;
 import java.util.SplittableRandom;
 import java.util.concurrent.ThreadLocalRandom;
 
-import org.apache.commons.collections4.bloomfilter.Hasher.IndexFilter;
+import org.apache.commons.collections4.bloomfilter.IndexFilter;
+import org.apache.commons.collections4.bloomfilter.IndexFilter.ArrayTracker;
+import org.apache.commons.collections4.bloomfilter.IndexFilter.BitMapTracker;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.CsvSource;