COLLECTIONS-831: Add BloomFilter clear() method

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

@@ -16,6 +16,7 @@
  */
 package org.apache.commons.collections4.bloomfilter;
 
+import java.util.Arrays;
 import java.util.Objects;
 import java.util.function.IntPredicate;
 import java.util.function.LongPredicate;
@@ -104,6 +105,11 @@ public final class ArrayCountingBloomFilter implements CountingBloomFilter {
         this.counts = source.counts.clone();
     }
 
+    @Override
+    public void clear() {
+        Arrays.fill(counts, 0);
+    }
+
     @Override
     public ArrayCountingBloomFilter copy() {
         return new ArrayCountingBloomFilter(this);

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

@@ -60,6 +60,11 @@ public interface BloomFilter extends IndexProducer, BitMapProducer {
      */
     Shape getShape();
 
+    /**
+     * Resets the filter to its initial, unpopulated state.
+     */
+    void clear();
+
     /**
      * Returns {@code true} if this filter contains the specified filter.
      *

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

@@ -117,6 +117,12 @@ public final class SimpleBloomFilter implements BloomFilter {
         this.cardinality = source.cardinality;
     }
 
+    @Override
+    public void clear() {
+        Arrays.fill(bitMap, 0L);
+        cardinality = 0;
+    }
+
     @Override
     public long[] asBitMapArray() {
         return Arrays.copyOf(bitMap, bitMap.length);

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

@@ -174,6 +174,11 @@ public final class SparseBloomFilter implements BloomFilter {
         return true;
     }
 
+    @Override
+    public void clear() {
+        indices.clear();
+    }
+
     @Override
     public Shape getShape() {
         return shape;

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

@@ -18,6 +18,7 @@ package org.apache.commons.collections4.bloomfilter;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -178,6 +179,14 @@ public abstract class AbstractBloomFilterTest<T extends BloomFilter> {
         assertTrue(bf4.contains(bf1));
     }
 
+    @Test
+    public void testClear() {
+        BloomFilter bf1 = createFilter(getTestShape(), from1);
+        assertNotEquals(0, bf1.cardinality());
+        bf1.clear();
+        assertEquals(0, bf1.cardinality());
+    }
+
     /**
      * Tests that the andCardinality calculations are correct.
      *

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

@@ -112,6 +112,11 @@ public class DefaultBloomFilterTest extends AbstractBloomFilterTest<DefaultBloom
             }
         }
 
+        @Override
+        public void clear() {
+            indices.clear();
+        }
+
         @Override
         public boolean forEachIndex(IntPredicate consumer) {
             for (Integer i : indices) {