diff --git a/src/test/java/org/apache/commons/lang3/HashSetvBitSetTest.java b/src/test/java/org/apache/commons/lang3/HashSetvBitSetTest.java new file mode 100644 index 000000000..07fcf5c99 --- /dev/null +++ b/src/test/java/org/apache/commons/lang3/HashSetvBitSetTest.java @@ -0,0 +1,112 @@ +/* + * 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.lang3; + +import java.util.BitSet; +import java.util.HashSet; + +import org.junit.Assert; +import org.junit.Test; + +/** + * Test to show whether using BitSet for removeAll() methods is faster than using HashSet. + */ +public class HashSetvBitSetTest { + + private static final int LOOPS = 2000; // number of times to invoke methods + + @Test + public void testTimes() { + timeHashSet(10); // warmup + timeBitSet(10); // warmup + printTimes(0); + printTimes(5); + printTimes(10); + printTimes(200); + printTimes(50); + printTimes(100); + printTimes(1000); + printTimes(2000); + } + private void printTimes(int count) { + long hashSet = timeHashSet(count); + long bitSet = timeBitSet(count); + // If percent is less than 100, then bitset is faster + System.out.println("Ratio="+(bitSet*100/hashSet)+"% count="+count+" hash="+hashSet+" bits="+bitSet); + } + + private static long timeHashSet(int count) { + int [] result = new int[0]; + long start = System.nanoTime(); + for (int i = 0; i < LOOPS; i++) { + result = testHashSet(count); + } + long elapsed = System.nanoTime() - start; + Assert.assertEquals(count, result.length); + return elapsed; + } + + private static long timeBitSet(int count) { + int [] result = new int[0]; + long start = System.nanoTime(); + for (int i = 0; i < LOOPS; i++) { + result = testBitSet(count); + } + long elapsed = System.nanoTime() - start; + Assert.assertEquals(count, result.length); + return elapsed; + } + + @SuppressWarnings("boxing") + private static int[] testHashSet(int count) { + HashSet toRemove = new HashSet(); + int found = 0; + for (int i = 0; i < count; i++) { + toRemove.add(found++); + } + return extractIndices(toRemove); + } + + private static int[] testBitSet(int count) { + BitSet toRemove = new BitSet(); + int found = 0; + for (int i = 0; i < count; i++) { + toRemove.set(found++); + } + return extractIndices(toRemove); + } + + + private static int[] extractIndices(HashSet coll) { + int[] result = new int[coll.size()]; + int i = 0; + for (Integer index : coll) { + result[i++] = index.intValue(); + } + return result; + } + + private static int[] extractIndices(BitSet coll) { + int[] result = new int[coll.cardinality()]; + int i = 0; + int j=0; + while((j=coll.nextSetBit(j)) != -1) { + result[i++] = j++; + } + return result; + } +} \ No newline at end of file