Fix generic typing for BloomFilter.copy()

Avoids guaranteed exceptions. For example:

SparseBloomFilter filter = new SimpleBloomFilter(Shape.fromNP(10000,
0.01)).copy();

After this commit, this type of broken code won't even compile.

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

@@ -160,6 +160,11 @@ public boolean contains(final IndexExtractor indexExtractor) {
         return indexExtractor.processIndices(idx -> cells[idx] != 0);
     }
 
+    /**
+     * Creates a new instance of this {@link ArrayCountingBloomFilter} with the same properties as the current one.
+     *
+     * @return a copy of this BloomFilter.
+     */
     @Override
     public ArrayCountingBloomFilter copy() {
         return new ArrayCountingBloomFilter(this);

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

@@ -23,11 +23,13 @@
  * <p>
  * <em>See implementation notes for {@link BitMapExtractor} and {@link IndexExtractor}.</em>
  * </p>
+ *
+ * @param <T> The BloomFilter type.
  * @see BitMapExtractor
  * @see IndexExtractor
  * @since 4.5.0
  */
-public interface BloomFilter extends IndexExtractor, BitMapExtractor {
+public interface BloomFilter<T extends BloomFilter<T>> extends IndexExtractor, BitMapExtractor {
 
     /**
      * The sparse characteristic used to determine the best method for matching.
@@ -84,7 +86,7 @@ default boolean contains(final BitMapExtractor bitMapExtractor) {
      * @param other the other Bloom filter
      * @return true if all enabled bits in the other filter are enabled in this filter.
      */
-    default boolean contains(final BloomFilter other) {
+    default boolean contains(final BloomFilter<?> other) {
         Objects.requireNonNull(other, "other");
         return (characteristics() & SPARSE) != 0 ? contains((IndexExtractor) other) : contains((BitMapExtractor) other);
     }
@@ -117,12 +119,11 @@ default boolean contains(final Hasher hasher) {
     boolean contains(IndexExtractor indexExtractor);
 
     /**
-     * Creates a new instance of the BloomFilter with the same properties as the current one.
+     * Creates a new instance of this {@link BloomFilter} with the same properties as the current one.
      *
-     * @param <T> Type of BloomFilter.
-     * @return a copy of this BloomFilter
+     * @return a copy of this {@link BloomFilter}.
      */
-    <T extends BloomFilter> T copy();
+    T copy();
 
     // update operations
 
@@ -142,7 +143,7 @@ default boolean contains(final Hasher hasher) {
      * @see #estimateN()
      * @see Shape
      */
-    default int estimateIntersection(final BloomFilter other) {
+    default int estimateIntersection(final BloomFilter<?> other) {
         Objects.requireNonNull(other, "other");
         final double eThis = getShape().estimateN(cardinality());
         final double eOther = getShape().estimateN(other.cardinality());
@@ -157,7 +158,7 @@ default int estimateIntersection(final BloomFilter other) {
         } else if (Double.isInfinite(eOther)) {
             estimate = Math.round(eThis);
         } else {
-            final BloomFilter union = this.copy();
+            final T union = this.copy();
             union.merge(other);
             final double eUnion = getShape().estimateN(union.cardinality());
             if (Double.isInfinite(eUnion)) {
@@ -220,11 +221,11 @@ default int estimateN() {
      * @see #estimateN()
      * @see Shape
      */
-    default int estimateUnion(final BloomFilter other) {
+    default int estimateUnion(final BloomFilter<?> other) {
         Objects.requireNonNull(other, "other");
-        final BloomFilter cpy = this.copy();
-        cpy.merge(other);
-        return cpy.estimateN();
+        final T copy = this.copy();
+        copy.merge(other);
+        return copy.estimateN();
     }
 
     /**
@@ -290,7 +291,7 @@ default boolean isFull() {
      * @param other The bloom filter to merge into this one.
      * @return true if the merge was successful
      */
-    default boolean merge(final BloomFilter other) {
+    default boolean merge(final BloomFilter<?> other) {
         return (characteristics() & SPARSE) != 0 ? merge((IndexExtractor) other) : merge((BitMapExtractor) other);
     }
 

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

@@ -41,12 +41,14 @@ public interface BloomFilterExtractor {
      * </ul>
      * <p><em>All modifications to the Bloom filters are reflected in the original filters</em></p>
      *
+     * @param <T> The BloomFilter type.
      * @param filters The filters to be returned by the extractor.
      * @return THe BloomFilterExtractor containing the filters.
      */
-    static BloomFilterExtractor fromBloomFilterArray(final BloomFilter... filters) {
+    static <T extends BloomFilter<T>> BloomFilterExtractor fromBloomFilterArray(final BloomFilter<?>... filters) {
         Objects.requireNonNull(filters, "filters");
         return new BloomFilterExtractor() {
+
             /**
              * This implementation returns a copy the original array, the contained Bloom filters
              * are references to the originals, any modifications to them are reflected in the original

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

@@ -54,7 +54,7 @@
  * @see CellExtractor
  * @since 4.5.0
  */
-public interface CountingBloomFilter extends BloomFilter, CellExtractor {
+public interface CountingBloomFilter extends BloomFilter<CountingBloomFilter>, CellExtractor {
 
     // Query Operations
 
@@ -74,13 +74,6 @@ public interface CountingBloomFilter extends BloomFilter, CellExtractor {
      */
     boolean add(CellExtractor other);
 
-    /**
-     * Creates a new instance of the CountingBloomFilter with the same properties as the current one.
-     * @return a copy of this CountingBloomFilter
-     */
-    @Override
-    CountingBloomFilter copy();
-
     /**
      * Returns the maximum allowable value for a cell count in this Counting filter.
      * @return the maximum allowable value for a cell count in this Counting filter.
@@ -114,7 +107,7 @@ default int getMaxInsert(final BitMapExtractor bitMapExtractor) {
      * @param bloomFilter the Bloom filter the check for.
      * @return the maximum number of times the Bloom filter could have been inserted.
      */
-    default int getMaxInsert(final BloomFilter bloomFilter) {
+    default int getMaxInsert(final BloomFilter<?> bloomFilter) {
         return getMaxInsert((BitMapExtractor) bloomFilter);
     }
 
@@ -204,7 +197,7 @@ default boolean merge(final BitMapExtractor bitMapExtractor) {
      * @see #add(CellExtractor)
      */
     @Override
-    default boolean merge(final BloomFilter other) {
+    default boolean merge(final BloomFilter<?> other) {
         Objects.requireNonNull(other, "other");
         return merge((IndexExtractor) other);
     }
@@ -288,7 +281,7 @@ default boolean remove(final BitMapExtractor bitMapExtractor) {
      * @see #isValid()
      * @see #subtract(CellExtractor)
      */
-    default boolean remove(final BloomFilter other) {
+    default boolean remove(final BloomFilter<?> other) {
         return remove((IndexExtractor) other);
     }
 

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

@@ -53,14 +53,14 @@
  * @param <T> the {@link BloomFilter} type.
  * @since 4.5.0
  */
-public class LayerManager<T extends BloomFilter> implements BloomFilterExtractor {
+public class LayerManager<T extends BloomFilter<T>> implements BloomFilterExtractor {
 
     /**
      * Builds new instances of {@link LayerManager}.
      *
      * @param <T> the {@link BloomFilter} type.
      */
-    public static class Builder<T extends BloomFilter> implements Supplier<LayerManager<T>> {
+    public static class Builder<T extends BloomFilter<T>> implements Supplier<LayerManager<T>> {
 
         private Predicate<LayerManager<T>> extendCheck;
         private Supplier<T> supplier;
@@ -131,7 +131,7 @@ public static final class Cleanup {
          * @param <T> Type of BloomFilter.
          * @return A Consumer suitable for the LayerManager {@code cleanup} parameter.
          */
-        public static <T extends BloomFilter> Consumer<Deque<T>> noCleanup() {
+        public static <T extends BloomFilter<T>> Consumer<Deque<T>> noCleanup() {
             return x -> {
                 // empty
             };
@@ -147,7 +147,7 @@ public static <T extends BloomFilter> Consumer<Deque<T>> noCleanup() {
          * @return A Consumer suitable for the LayerManager {@code cleanup} parameter.
          * @throws IllegalArgumentException if {@code maxSize <= 0}.
          */
-        public static <T extends BloomFilter> Consumer<Deque<T>> onMaxSize(final int maxSize) {
+        public static <T extends BloomFilter<T>> Consumer<Deque<T>> onMaxSize(final int maxSize) {
             if (maxSize <= 0) {
                 throw new IllegalArgumentException("'maxSize' must be greater than 0");
             }
@@ -165,7 +165,7 @@ public static <T extends BloomFilter> Consumer<Deque<T>> onMaxSize(final int max
          * @param <T> Type of BloomFilter.
          * @return A Consumer suitable for the LayerManager {@code cleanup} parameter.
          */
-        public static <T extends BloomFilter> Consumer<Deque<T>> removeEmptyTarget() {
+        public static <T extends BloomFilter<T>> Consumer<Deque<T>> removeEmptyTarget() {
             return x -> {
                 if (!x.isEmpty() && x.getLast().isEmpty()) {
                     x.removeLast();
@@ -180,7 +180,7 @@ public static <T extends BloomFilter> Consumer<Deque<T>> removeEmptyTarget() {
          * @param test Predicate.
          * @return A Consumer suitable for the LayerManager {@code cleanup} parameter.
          */
-        public static <T extends BloomFilter> Consumer<Deque<T>> removeIf(final Predicate<? super T> test) {
+        public static <T extends BloomFilter<T>> Consumer<Deque<T>> removeIf(final Predicate<? super T> test) {
             return x -> x.removeIf(test);
         }
 
@@ -202,7 +202,7 @@ public static final class ExtendCheck {
          * @return A Predicate suitable for the LayerManager {@code extendCheck} parameter.
          * @throws IllegalArgumentException if {@code breakAt <= 0}
          */
-        public static <T extends BloomFilter> Predicate<LayerManager<T>> advanceOnCount(final int breakAt) {
+        public static <T extends BloomFilter<T>> Predicate<LayerManager<T>> advanceOnCount(final int breakAt) {
             if (breakAt <= 0) {
                 throw new IllegalArgumentException("'breakAt' must be greater than 0");
             }
@@ -226,7 +226,7 @@ public boolean test(final LayerManager<T> filter) {
          * @param <T> Type of BloomFilter.
          * @return A Predicate suitable for the LayerManager {@code extendCheck} parameter.
          */
-        public static <T extends BloomFilter> Predicate<LayerManager<T>> advanceOnPopulated() {
+        public static <T extends BloomFilter<T>> Predicate<LayerManager<T>> advanceOnPopulated() {
             return lm -> !lm.last().isEmpty();
         }
 
@@ -242,12 +242,12 @@ public static <T extends BloomFilter> Predicate<LayerManager<T>> advanceOnPopula
          * @return A Predicate suitable for the LayerManager {@code extendCheck} parameter.
          * @throws IllegalArgumentException if {@code maxN <= 0}
          */
-        public static <T extends BloomFilter> Predicate<LayerManager<T>> advanceOnSaturation(final double maxN) {
+        public static <T extends BloomFilter<T>> Predicate<LayerManager<T>> advanceOnSaturation(final double maxN) {
             if (maxN <= 0) {
                 throw new IllegalArgumentException("'maxN' must be greater than 0");
             }
             return manager -> {
-                final BloomFilter bf = manager.last();
+                final T bf = manager.last();
                 return maxN <= bf.getShape().estimateN(bf.cardinality());
             };
         }
@@ -259,13 +259,14 @@ public static <T extends BloomFilter> Predicate<LayerManager<T>> advanceOnSatura
          * @param <T> Type of BloomFilter.
          * @return A Predicate suitable for the LayerManager {@code extendCheck} parameter.
          */
-        public static <T extends BloomFilter> Predicate<LayerManager<T>> neverAdvance() {
+        public static <T extends BloomFilter<T>> Predicate<LayerManager<T>> neverAdvance() {
             return x -> false;
         }
 
         private ExtendCheck() {
         }
     }
+
     /**
      * Creates a new Builder with defaults of {@code ExtendCheck.neverAdvance()} and
      * {@code Cleanup.noCleanup()}.
@@ -275,7 +276,7 @@ private ExtendCheck() {
      * @see ExtendCheck#neverAdvance()
      * @see Cleanup#noCleanup()
      */
-    public static <T extends BloomFilter> Builder<T> builder() {
+    public static <T extends BloomFilter<T>> Builder<T> builder() {
         return new Builder<>();
     }
 
@@ -337,13 +338,15 @@ public final void clear() {
     }
 
     /**
-     * Creates a deep copy of this LayerManager.
-     * <p><em>Filters in the copy are deep copies, not references, so changes in the copy
-     * are NOT reflected in the original.</em></p>
-     * <p>The {@code filterSupplier}, {@code extendCheck}, and the {@code filterCleanup} are shared between
-     * the copy and this instance.</p>
+     * Creates a deep copy of this {@link LayerManager}.
+     * <p>
+     * <em>Filters in the copy are deep copies, not references, so changes in the copy are NOT reflected in the original.</em>
+     * </p>
+     * <p>
+     * The {@code filterSupplier}, {@code extendCheck}, and the {@code filterCleanup} are shared between the copy and this instance.
+     * </p>
      *
-     * @return a copy of this layer Manager.
+     * @return a copy of this {@link LayerManager}.
      */
     public LayerManager<T> copy() {
         final LayerManager<T> newMgr = new LayerManager<>(filterSupplier, extendCheck, filterCleanup, false);
@@ -438,7 +441,7 @@ void next() {
      */
     @Override
     public boolean processBloomFilters(final Predicate<BloomFilter> bloomFilterPredicate) {
-        for (final BloomFilter bf : filters) {
+        for (final T bf : filters) {
             if (!bloomFilterPredicate.test(bf)) {
                 return false;
             }

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

@@ -59,20 +59,21 @@
  * removes them. It also checks it a new layer should be added, and if so adds
  * it and sets the {@code target} before the operation.</li>
  * </ul>
+ *
  * @param <T> The type of Bloom Filter that is used for the layers.
  * @since 4.5.0
  */
-public class LayeredBloomFilter<T extends BloomFilter> implements BloomFilter, BloomFilterExtractor {
+public class LayeredBloomFilter<T extends BloomFilter<T>> implements BloomFilter<LayeredBloomFilter<T>>, BloomFilterExtractor {
     /**
      * A class used to locate matching filters across all the layers.
      */
     private class Finder implements Predicate<BloomFilter> {
         int[] result = new int[layerManager.getDepth()];
         int bfIdx;
         int resultIdx;
-        BloomFilter bf;
+        BloomFilter<?> bf;
 
-        Finder(final BloomFilter bf) {
+        Finder(final BloomFilter<?> bf) {
             this.bf = bf;
         }
 
@@ -180,6 +181,11 @@ public boolean contains(final IndexExtractor indexExtractor) {
         return contains(createFilter(indexExtractor));
     }
 
+    /**
+     * Creates a new instance of this {@link LayeredBloomFilter} with the same properties as the current one.
+     *
+     * @return a copy of this {@link LayeredBloomFilter}.
+     */
     @Override
     public LayeredBloomFilter<T> copy() {
         return new LayeredBloomFilter<>(shape, layerManager.copy());
@@ -191,7 +197,7 @@ public LayeredBloomFilter<T> copy() {
      * @param bitMapExtractor the BitMapExtractor to create the filter from.
      * @return the BloomFilter.
      */
-    private BloomFilter createFilter(final BitMapExtractor bitMapExtractor) {
+    private SimpleBloomFilter createFilter(final BitMapExtractor bitMapExtractor) {
         final SimpleBloomFilter bf = new SimpleBloomFilter(shape);
         bf.merge(bitMapExtractor);
         return bf;
@@ -203,7 +209,7 @@ private BloomFilter createFilter(final BitMapExtractor bitMapExtractor) {
      * @param hasher the hasher to create the filter from.
      * @return the BloomFilter.
      */
-    private BloomFilter createFilter(final Hasher hasher) {
+    private SimpleBloomFilter createFilter(final Hasher hasher) {
         final SimpleBloomFilter bf = new SimpleBloomFilter(shape);
         bf.merge(hasher);
         return bf;
@@ -215,7 +221,7 @@ private BloomFilter createFilter(final Hasher hasher) {
      * @param indexExtractor the IndexExtractor to create the filter from.
      * @return the BloomFilter.
      */
-    private BloomFilter createFilter(final IndexExtractor indexExtractor) {
+    private SimpleBloomFilter createFilter(final IndexExtractor indexExtractor) {
         final SimpleBloomFilter bf = new SimpleBloomFilter(shape);
         bf.merge(indexExtractor);
         return bf;
@@ -289,8 +295,8 @@ public int[] find(final IndexExtractor indexExtractor) {
      * @return the merged bloom filter.
      */
     @Override
-    public BloomFilter flatten() {
-        final BloomFilter bf = new SimpleBloomFilter(shape);
+    public SimpleBloomFilter flatten() {
+        final SimpleBloomFilter bf = new SimpleBloomFilter(shape);
         processBloomFilters(bf::merge);
         return bf;
     }

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

@@ -112,7 +112,7 @@ public static double cosineSimilarity(final BitMapExtractor first, final BitMapE
      * @param second the second Bloom filter.
      * @return the Cosine similarity.
      */
-    public static double cosineSimilarity(final BloomFilter first, final BloomFilter second) {
+    public static double cosineSimilarity(final BloomFilter<?> first, final BloomFilter<?> second) {
         final int numerator = andCardinality(first, second);
         // Given that the cardinality is an int then the product as a double will not
         // overflow, we can use one sqrt: