moved thread local random examples from core-java-concurrency-advanced to core-java-concurrency-advanced-2

core-java-modules/core-java-concurrency-advanced-2/README.md

@@ -10,3 +10,4 @@
 - [Print Even and Odd Numbers Using 2 Threads](https://www.baeldung.com/java-even-odd-numbers-with-2-threads)
 - [Java CyclicBarrier vs CountDownLatch](https://www.baeldung.com/java-cyclicbarrier-countdownlatch)
 - [Guide to the Fork/Join Framework in Java](https://www.baeldung.com/java-fork-join)
+- [Guide to ThreadLocalRandom in Java](https://www.baeldung.com/java-thread-local-random)

core-java-modules/core-java-concurrency-advanced-2/pom.xml

@@ -20,6 +20,16 @@
             <artifactId>commons-lang3</artifactId>
             <version>${commons-lang3.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh-core.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh-generator-annprocess.version}</version>
+        </dependency>
         
         <dependency>
             <groupId>org.assertj</groupId>
@@ -40,6 +50,9 @@
     </build>
 
     <properties>
+        <jmh-core.version>1.19</jmh-core.version>
+        <jmh-generator-annprocess.version>1.19</jmh-generator-annprocess.version>
+        
         <assertj.version>3.6.1</assertj.version>
     </properties>
 

core-java-modules/core-java-concurrency-advanced-2/src/main/java/com/baeldung/threadlocalrandom/ThreadLocalRandomBenchMarkRunner.java

@@ -0,0 +1,22 @@
+package com.baeldung.threadlocalrandom;
+
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+public class ThreadLocalRandomBenchMarkRunner {
+
+    public static void main(String[] args) throws Exception {
+
+        Options options = new OptionsBuilder().include(ThreadLocalRandomBenchMarker.class.getSimpleName())
+            .threads(1)
+            .forks(1)
+            .shouldFailOnError(true)
+            .shouldDoGC(true)
+            .jvmArgs("-server")
+            .build();
+
+        new Runner(options).run();
+
+    }
+}

core-java-modules/core-java-concurrency-advanced-2/src/main/java/com/baeldung/threadlocalrandom/ThreadLocalRandomBenchMarker.java

@@ -0,0 +1,64 @@
+package com.baeldung.threadlocalrandom;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.concurrent.TimeUnit;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+
+@BenchmarkMode(Mode.AverageTime)
+@Warmup(iterations = 1)
+@OutputTimeUnit(TimeUnit.MICROSECONDS)
+@State(Scope.Benchmark)
+public class ThreadLocalRandomBenchMarker {
+
+    List<Callable<Integer>> randomCallables = new ArrayList<>();
+    List<Callable<Integer>> threadLocalRandomCallables = new ArrayList<>();
+
+    @Setup(Level.Iteration)
+    public void init() {
+        Random random = new Random();
+        randomCallables = new ArrayList<>();
+        threadLocalRandomCallables = new ArrayList<>();
+        for (int i = 0; i < 1000; i++) {
+            randomCallables.add(() -> {
+                return random.nextInt();
+            });
+        }
+
+        for (int i = 0; i < 1000; i++) {
+            threadLocalRandomCallables.add(() -> {
+                return ThreadLocalRandom.current()
+                    .nextInt();
+            });
+        }
+    }
+
+    @Benchmark
+    public void randomValuesUsingRandom() throws InterruptedException {
+        ExecutorService executor = Executors.newWorkStealingPool();
+        executor.invokeAll(randomCallables);
+        executor.shutdown();
+    }
+
+    @Benchmark
+    public void randomValuesUsingThreadLocalRandom() throws InterruptedException {
+        ExecutorService executor = Executors.newWorkStealingPool();
+        executor.invokeAll(threadLocalRandomCallables);
+        executor.shutdown();
+    }
+
+}

core-java-modules/core-java-concurrency-advanced-2/src/test/java/com/baeldung/threadlocalrandom/ThreadLocalRandomIntegrationTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.threadlocalrandom;
+
+import java.util.concurrent.ThreadLocalRandom;
+
+import static org.junit.Assert.assertTrue;
+import org.junit.Test;
+
+public class ThreadLocalRandomIntegrationTest {
+    
+    @Test
+    public void givenUsingThreadLocalRandom_whenGeneratingRandomIntBounded_thenCorrect() {
+        int leftLimit = 1;
+        int rightLimit = 100;
+        int generatedInt = ThreadLocalRandom.current().nextInt(leftLimit, rightLimit);
+        
+        assertTrue(generatedInt < rightLimit && generatedInt >= leftLimit);
+    }
+    
+    @Test
+    public void givenUsingThreadLocalRandom_whenGeneratingRandomIntUnbounded_thenCorrect() {
+        int generatedInt = ThreadLocalRandom.current().nextInt();
+        
+        assertTrue(generatedInt < Integer.MAX_VALUE && generatedInt >= Integer.MIN_VALUE);
+    }
+    
+    @Test
+    public void givenUsingThreadLocalRandom_whenGeneratingRandomLongBounded_thenCorrect() {
+        long leftLimit = 1L;
+        long rightLimit = 100L;
+        long generatedLong = ThreadLocalRandom.current().nextLong(leftLimit, rightLimit);
+        
+        assertTrue(generatedLong < rightLimit && generatedLong >= leftLimit);
+    }
+    
+    @Test
+    public void givenUsingThreadLocalRandom_whenGeneratingRandomLongUnbounded_thenCorrect() {
+        long generatedInt = ThreadLocalRandom.current().nextLong();
+        
+        assertTrue(generatedInt < Long.MAX_VALUE && generatedInt >= Long.MIN_VALUE);
+    }
+    
+    @Test
+    public void givenUsingThreadLocalRandom_whenGeneratingRandomDoubleBounded_thenCorrect() {
+        double leftLimit = 1D;
+        double rightLimit = 100D;
+        double generatedInt = ThreadLocalRandom.current().nextDouble(leftLimit, rightLimit);
+        
+        assertTrue(generatedInt < rightLimit && generatedInt >= leftLimit);
+    }
+    
+    @Test
+    public void givenUsingThreadLocalRandom_whenGeneratingRandomDoubleUnbounded_thenCorrect() {
+        double generatedInt = ThreadLocalRandom.current().nextDouble();
+        
+        assertTrue(generatedInt < Double.MAX_VALUE && generatedInt >= Double.MIN_VALUE);
+    }
+    
+    @Test(expected = UnsupportedOperationException.class)
+    public void givenUsingThreadLocalRandom_whenSettingSeed_thenThrowUnsupportedOperationException() {
+        ThreadLocalRandom.current().setSeed(0l);
+    }
+
+}