[GitHub] [kafka] ruanwenjun commented on a change in pull request #11754: MINOR: Optimize collection method in Utils

[GitBox <gi...@apache.org>]

ruanwenjun commented on a change in pull request #11754:
URL: https://github.com/apache/kafka/pull/11754#discussion_r805769215



##########
File path: clients/src/main/java/org/apache/kafka/common/utils/Utils.java
##########
@@ -764,10 +764,7 @@ public static ByteBuffer ensureCapacity(ByteBuffer existingBuffer, int newLength
      */
     @SafeVarargs
     public static <T> Set<T> mkSet(T... elems) {
-        Set<T> result = new HashSet<>((int) (elems.length / 0.75) + 1);
-        for (T elem : elems)
-            result.add(elem);
-        return result;
+        return new HashSet<>(Arrays.asList(elems));

Review comment:
       Yes, I got your concern. The `Arrays.asList(elems) ` just copy the reference of elems.
   And I create a benchmark test looks like below
   ```java
   @State(Scope.Benchmark)
   @Fork(value = 1)
   @Warmup(iterations = 3)
   @Measurement(iterations = 10)
   @BenchmarkMode(Mode.AverageTime)
   @OutputTimeUnit(TimeUnit.MILLISECONDS)
   public class CreateSetTest {
   
       private int[] inits = new int[100];
   
       @Setup(Level.Trial)
       public void setUp() {
           for (int i = 0; i < inits.length; i++) {
               inits[i] = ThreadLocalRandom.current().nextInt();
           }
       }
   
       @Benchmark
       public void testCreateHashSet1() {
           HashSet<int[]> ints = new HashSet<>(Arrays.asList(inits));
       }
   
       @Benchmark
       public void testCreateHashSet2() {
           Set<Integer> result = new HashSet<>((int) (inits.length / 0.75) + 1);
           for (Integer elem : inits)
               result.add(elem);
       }
   
   
       public static void main(String[] args) throws RunnerException {
           Options opt = new OptionsBuilder()
               .include(CreateSetTest.class.getSimpleName())
               .forks(2)
               .build();
   
           new Runner(opt).run();
       }
   }
   ```
   
   The test result 
   ```
   Benchmark                Mode  Cnt   Score    Error  Units
   CreateSetTest.testCreateHashSet1  avgt   20  ≈ 10⁻⁴           ms/op
   CreateSetTest.testCreateHashSet2  avgt   20   0.001 ±  0.001  ms/op
   ```
   
   It seems it will not cause performance reduce.




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