Merge branch 'master' into master

2019-01-11 11:16:57 -05:00
parent 81e2750ee0 36e4892446
commit 2c80343944
93 changed files with 1920 additions and 286 deletions
@@ -14,3 +14,4 @@
 - [Calculate Factorial in Java](https://www.baeldung.com/java-calculate-factorial)
 - [Find Substrings That Are Palindromes in Java](https://www.baeldung.com/java-palindrome-substrings)
 - [Find the Longest Substring without Repeating Characters](https://www.baeldung.com/java-longest-substring-without-repeated-characters)
+- [Java Two Pointer Technique](https://www.baeldung.com/java-two-pointer-technique)
@@ -6,7 +6,6 @@ import static com.datastax.spark.connector.japi.CassandraJavaUtil.mapToRow;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.HashMap;
-import java.util.Iterator;
 import java.util.List;
 import java.util.Map;

@@ -15,13 +14,7 @@ import org.apache.kafka.common.serialization.StringDeserializer;
 import org.apache.log4j.Level;
 import org.apache.log4j.Logger;
 import org.apache.spark.SparkConf;
-import org.apache.spark.api.java.JavaPairRDD;
 import org.apache.spark.api.java.JavaRDD;
-import org.apache.spark.api.java.function.FlatMapFunction;
-import org.apache.spark.api.java.function.Function;
-import org.apache.spark.api.java.function.Function2;
-import org.apache.spark.api.java.function.PairFunction;
-import org.apache.spark.api.java.function.VoidFunction;
 import org.apache.spark.streaming.Durations;
 import org.apache.spark.streaming.api.java.JavaDStream;
 import org.apache.spark.streaming.api.java.JavaInputDStream;
@@ -35,7 +28,6 @@ import scala.Tuple2;

 public class WordCountingApp {

-    @SuppressWarnings("serial")
    public static void main(String[] args) throws InterruptedException {
        Logger.getLogger("org")
            .setLevel(Level.OFF);
@@ -61,52 +53,24 @@ public class WordCountingApp {

        JavaInputDStream<ConsumerRecord<String, String>> messages = KafkaUtils.createDirectStream(streamingContext, LocationStrategies.PreferConsistent(), ConsumerStrategies.<String, String> Subscribe(topics, kafkaParams));

-        JavaPairDStream<String, String> results = messages.mapToPair(new PairFunction<ConsumerRecord<String, String>, String, String>() {
-            @Override
-            public Tuple2<String, String> call(ConsumerRecord<String, String> record) {
-                return new Tuple2<>(record.key(), record.value());
-            }
-        });
+        JavaPairDStream<String, String> results = messages.mapToPair(record -> new Tuple2<>(record.key(), record.value()));

-        JavaDStream<String> lines = results.map(new Function<Tuple2<String, String>, String>() {
-            @Override
-            public String call(Tuple2<String, String> tuple2) {
-                return tuple2._2();
-            }
-        });
+        JavaDStream<String> lines = results.map(tuple2 -> tuple2._2());

-        JavaDStream<String> words = lines.flatMap(new FlatMapFunction<String, String>() {
-            @Override
-            public Iterator<String> call(String x) {
-                return Arrays.asList(x.split("\\s+"))
-                    .iterator();
-            }
-        });
+        JavaDStream<String> words = lines.flatMap(x -> Arrays.asList(x.split("\\s+"))
+            .iterator());

-        JavaPairDStream<String, Integer> wordCounts = words.mapToPair(new PairFunction<String, String, Integer>() {
-            @Override
-            public Tuple2<String, Integer> call(String s) {
-                return new Tuple2<>(s, 1);
-            }
-        })
-            .reduceByKey(new Function2<Integer, Integer, Integer>() {
-                @Override
-                public Integer call(Integer i1, Integer i2) {
-                    return i1 + i2;
-                }
-            });
+        JavaPairDStream<String, Integer> wordCounts = words.mapToPair(s -> new Tuple2<>(s, 1))
+            .reduceByKey((i1, i2) -> i1 + i2);

-        wordCounts.foreachRDD(new VoidFunction<JavaPairRDD<String, Integer>>() {
-            @Override
-            public void call(JavaPairRDD<String, Integer> javaRdd) throws Exception {
-                Map<String, Integer> wordCountMap = javaRdd.collectAsMap();
-                for (String key : wordCountMap.keySet()) {
-                    List<Word> words = Arrays.asList(new Word(key, wordCountMap.get(key)));
-                    JavaRDD<Word> rdd = streamingContext.sparkContext()
-                        .parallelize(words);
-                    javaFunctions(rdd).writerBuilder("vocabulary", "words", mapToRow(Word.class))
-                        .saveToCassandra();
-                }
+        wordCounts.foreachRDD(javaRdd -> {
+            Map<String, Integer> wordCountMap = javaRdd.collectAsMap();
+            for (String key : wordCountMap.keySet()) {
+                List<Word> wordList = Arrays.asList(new Word(key, wordCountMap.get(key)));
+                JavaRDD<Word> rdd = streamingContext.sparkContext()
+                    .parallelize(wordList);
+                javaFunctions(rdd).writerBuilder("vocabulary", "words", mapToRow(Word.class))
+                    .saveToCassandra();
            }
        });

@@ -6,7 +6,6 @@ import static com.datastax.spark.connector.japi.CassandraJavaUtil.mapToRow;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.HashMap;
-import java.util.Iterator;
 import java.util.List;
 import java.util.Map;

@@ -15,18 +14,10 @@ import org.apache.kafka.common.serialization.StringDeserializer;
 import org.apache.log4j.Level;
 import org.apache.log4j.Logger;
 import org.apache.spark.SparkConf;
-import org.apache.spark.api.java.JavaPairRDD;
 import org.apache.spark.api.java.JavaRDD;
 import org.apache.spark.api.java.JavaSparkContext;
-import org.apache.spark.api.java.Optional;
-import org.apache.spark.api.java.function.FlatMapFunction;
-import org.apache.spark.api.java.function.Function;
 import org.apache.spark.api.java.function.Function2;
-import org.apache.spark.api.java.function.Function3;
-import org.apache.spark.api.java.function.PairFunction;
-import org.apache.spark.api.java.function.VoidFunction;
 import org.apache.spark.streaming.Durations;
-import org.apache.spark.streaming.State;
 import org.apache.spark.streaming.StateSpec;
 import org.apache.spark.streaming.api.java.JavaDStream;
 import org.apache.spark.streaming.api.java.JavaInputDStream;
@@ -43,7 +34,6 @@ public class WordCountingAppWithCheckpoint {

    public static JavaSparkContext sparkContext;

-    @SuppressWarnings("serial")
    public static void main(String[] args) throws InterruptedException {

        Logger.getLogger("org")
@@ -74,63 +64,30 @@ public class WordCountingAppWithCheckpoint {

        JavaInputDStream<ConsumerRecord<String, String>> messages = KafkaUtils.createDirectStream(streamingContext, LocationStrategies.PreferConsistent(), ConsumerStrategies.<String, String> Subscribe(topics, kafkaParams));

-        JavaPairDStream<String, String> results = messages.mapToPair(new PairFunction<ConsumerRecord<String, String>, String, String>() {
-            @Override
-            public Tuple2<String, String> call(ConsumerRecord<String, String> record) {
-                return new Tuple2<>(record.key(), record.value());
-            }
-        });
+        JavaPairDStream<String, String> results = messages.mapToPair(record -> new Tuple2<>(record.key(), record.value()));

-        JavaDStream<String> lines = results.map(new Function<Tuple2<String, String>, String>() {
-            @Override
-            public String call(Tuple2<String, String> tuple2) {
-                return tuple2._2();
-            }
-        });
+        JavaDStream<String> lines = results.map(tuple2 -> tuple2._2());

-        JavaDStream<String> words = lines.flatMap(new FlatMapFunction<String, String>() {
-            @Override
-            public Iterator<String> call(String x) {
-                return Arrays.asList(x.split("\\s+"))
-                    .iterator();
-            }
-        });
+        JavaDStream<String> words = lines.flatMap(x -> Arrays.asList(x.split("\\s+"))
+            .iterator());

-        JavaPairDStream<String, Integer> wordCounts = words.mapToPair(new PairFunction<String, String, Integer>() {
-            @Override
-            public Tuple2<String, Integer> call(String s) {
-                return new Tuple2<>(s, 1);
-            }
-        })
-            .reduceByKey(new Function2<Integer, Integer, Integer>() {
-                @Override
-                public Integer call(Integer i1, Integer i2) {
-                    return i1 + i2;
-                }
-            });
+        JavaPairDStream<String, Integer> wordCounts = words.mapToPair(s -> new Tuple2<>(s, 1))
+            .reduceByKey((Function2<Integer, Integer, Integer>) (i1, i2) -> i1 + i2);

-        Function3<String, Optional<Integer>, State<Integer>, Tuple2<String, Integer>> mappingFunc = (word, one, state) -> {
+        JavaMapWithStateDStream<String, Integer, Integer, Tuple2<String, Integer>> cumulativeWordCounts = wordCounts.mapWithState(StateSpec.function((word, one, state) -> {
            int sum = one.orElse(0) + (state.exists() ? state.get() : 0);
            Tuple2<String, Integer> output = new Tuple2<>(word, sum);
            state.update(sum);
            return output;
-        };
+        }));

-        JavaPairRDD<String, Integer> initialRDD = JavaPairRDD.fromJavaRDD(sparkContext.emptyRDD());
-
-        JavaMapWithStateDStream<String, Integer, Integer, Tuple2<String, Integer>> cumulativeWordCounts = wordCounts.mapWithState(StateSpec.function(mappingFunc)
-            .initialState(initialRDD));
-
-        cumulativeWordCounts.foreachRDD(new VoidFunction<JavaRDD<Tuple2<String, Integer>>>() {
-            @Override
-            public void call(JavaRDD<Tuple2<String, Integer>> javaRdd) throws Exception {
-                List<Tuple2<String, Integer>> wordCountList = javaRdd.collect();
-                for (Tuple2<String, Integer> tuple : wordCountList) {
-                    List<Word> words = Arrays.asList(new Word(tuple._1, tuple._2));
-                    JavaRDD<Word> rdd = sparkContext.parallelize(words);
-                    javaFunctions(rdd).writerBuilder("vocabulary", "words", mapToRow(Word.class))
-                        .saveToCassandra();
-                }
+        cumulativeWordCounts.foreachRDD(javaRdd -> {
+            List<Tuple2<String, Integer>> wordCountList = javaRdd.collect();
+            for (Tuple2<String, Integer> tuple : wordCountList) {
+                List<Word> wordList = Arrays.asList(new Word(tuple._1, tuple._2));
+                JavaRDD<Word> rdd = sparkContext.parallelize(wordList);
+                javaFunctions(rdd).writerBuilder("vocabulary", "words", mapToRow(Word.class))
+                    .saveToCassandra();
            }
        });

@@ -0,0 +1,27 @@
+package com.baeldung.java.list;
+
+import java.util.Enumeration;
+import java.util.Iterator;
+import java.util.Vector;
+
+public class VectorExample {
+
+    public static void main(String[] args) {
+
+        Vector<String> vector = new Vector<>();
+        vector.add("baeldung");
+        vector.add("Vector");
+        vector.add("example");
+
+        Enumeration e = vector.elements();
+        while(e.hasMoreElements()){
+            System.out.println(e.nextElement());
+        }
+
+        Iterator<String> iterator = vector.iterator();
+        while (iterator.hasNext()) {
+            System.out.println(iterator.next());
+        }
+    }
+
+}
@@ -9,7 +9,7 @@ import java.util.*;
 import java.util.concurrent.TimeUnit;

@BenchmarkMode(Mode.AverageTime)
-@OutputTimeUnit(TimeUnit.MICROSECONDS)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Warmup(iterations = 10)
 public class ArrayListBenchmark {

@@ -17,6 +17,7 @@ public class ArrayListBenchmark {
    public static class MyState {

        List<Employee> employeeList = new ArrayList<>();
+        Vector<Employee> employeeVector = new Vector<>();
        //LinkedList<Employee> employeeList = new LinkedList<>();

        long iterations = 100000;
@@ -29,9 +30,11 @@ public class ArrayListBenchmark {
        public void setUp() {
            for (long i = 0; i < iterations; i++) {
                employeeList.add(new Employee(i, "John"));
+                employeeVector.add(new Employee(i, "John"));
            }

            employeeList.add(employee);
+            employeeVector.add(employee);
            employeeIndex = employeeList.indexOf(employee);
        }
    }
@@ -46,6 +49,11 @@ public class ArrayListBenchmark {
        return state.employeeList.contains(state.employee);
    }

+    @Benchmark
+    public boolean testContainsVector(ArrayListBenchmark.MyState state) {
+        return state.employeeVector.contains(state.employee);
+    }
+
    @Benchmark
    public int testIndexOf(ArrayListBenchmark.MyState state) {
        return state.employeeList.indexOf(state.employee);
@@ -56,19 +64,24 @@ public class ArrayListBenchmark {
        return state.employeeList.get(state.employeeIndex);
    }

+    @Benchmark
+    public Employee testVectorGet(ArrayListBenchmark.MyState state) {
+        return state.employeeVector.get(state.employeeIndex);
+    }
+
    @Benchmark
    public boolean testRemove(ArrayListBenchmark.MyState state) {
        return state.employeeList.remove(state.employee);
    }

-//    @Benchmark
-//    public void testAdd(ArrayListBenchmark.MyState state) {
-//        state.employeeList.add(new Employee(state.iterations + 1, "John"));
-//    }
+    @Benchmark
+    public void testAdd(ArrayListBenchmark.MyState state) {
+        state.employeeList.add(new Employee(state.iterations + 1, "John"));
+    }

    public static void main(String[] args) throws Exception {
        Options options = new OptionsBuilder()
-                .include(ArrayListBenchmark.class.getSimpleName()).threads(1)
+                .include(ArrayListBenchmark.class.getSimpleName()).threads(3)
                .forks(1).shouldFailOnError(true)
                .shouldDoGC(true)
                .jvmArgs("-server").build();
@@ -0,0 +1,48 @@
+package com.baeldung.queueinterface;
+
+import java.util.AbstractQueue;
+import java.util.Iterator;
+import java.util.LinkedList;
+
+public class CustomBaeldungQueue<T> extends AbstractQueue<T> {
+
+  private LinkedList<T> elements;
+
+  public CustomBaeldungQueue() {
+    this.elements = new LinkedList<T>();
+  }
+
+  @Override
+  public Iterator<T> iterator() {
+    return elements.iterator();
+  }
+
+  @Override
+  public int size() {
+    return elements.size();
+  }
+
+  @Override
+  public boolean offer(T t) {
+    if(t == null) return false;
+    elements.add(t);
+    return true;
+  }
+
+  @Override
+  public T poll() {
+
+    Iterator<T> iter = elements.iterator();
+    T t = iter.next();
+    if(t != null){
+      iter.remove();
+      return t;
+    }
+    return null;
+  }
+
+  @Override
+  public T peek() {
+    return elements.getFirst();
+  }
+}
@@ -0,0 +1,53 @@
+package com.baeldung.queueinterface;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.PriorityQueue;
+
+import static org.junit.Assert.assertEquals;
+
+public class PriorityQueueUnitTest {
+
+
+
+  @Test
+  public void givenIntegerQueue_whenIntegersOutOfOrder_checkRetrievalOrderIsNatural() {
+
+    PriorityQueue<Integer> integerQueue = new PriorityQueue<>();
+
+    integerQueue.add(9);
+    integerQueue.add(2);
+    integerQueue.add(4);
+
+    int first = integerQueue.poll();
+    int second = integerQueue.poll();
+    int third = integerQueue.poll();
+
+    assertEquals(2, first);
+    assertEquals(4, second);
+    assertEquals(9, third);
+
+
+  }
+
+  @Test
+  public void givenStringQueue_whenStringsAddedOutOfNaturalOrder_checkRetrievalOrderNatural() {
+
+    PriorityQueue<String> stringQueue = new PriorityQueue<>();
+
+    stringQueue.add("banana");
+    stringQueue.add("apple");
+    stringQueue.add("cherry");
+
+    String first = stringQueue.poll();
+    String second = stringQueue.poll();
+    String third = stringQueue.poll();
+
+    assertEquals("apple", first);
+    assertEquals("banana", second);
+    assertEquals("cherry", third);
+
+
+  }
+}
@@ -0,0 +1,30 @@
+package com.baeldung.queueinterface;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class CustomBaeldungQueueUnitTest {
+
+  private CustomBaeldungQueue<Integer> customQueue;
+
+  @Before
+  public void setUp() throws Exception {
+    customQueue = new CustomBaeldungQueue<>();
+  }
+
+  @Test
+  public void givenQueueWithTwoElements_whenElementsRetrieved_checkRetrievalCorrect() {
+
+    customQueue.add(7);
+    customQueue.add(5);
+
+    int first = customQueue.poll();
+    int second = customQueue.poll();
+
+    assertEquals(7, first);
+    assertEquals(5, second);
+
+  }
+}
@@ -0,0 +1,86 @@
+package com.baeldung.concurrent.threadsafety.application;
+
+import com.baeldung.concurrent.threadsafety.callables.AtomicCounterCallable;
+import com.baeldung.concurrent.threadsafety.mathutils.MathUtils;
+import com.baeldung.concurrent.threadsafety.callables.CounterCallable;
+import com.baeldung.concurrent.threadsafety.callables.ExtrinsicLockCounterCallable;
+import com.baeldung.concurrent.threadsafety.callables.MessageServiceCallable;
+import com.baeldung.concurrent.threadsafety.callables.ReentranReadWriteLockCounterCallable;
+import com.baeldung.concurrent.threadsafety.callables.ReentrantLockCounterCallable;
+import com.baeldung.concurrent.threadsafety.services.AtomicCounter;
+import com.baeldung.concurrent.threadsafety.services.Counter;
+import com.baeldung.concurrent.threadsafety.services.ExtrinsicLockCounter;
+import com.baeldung.concurrent.threadsafety.services.MessageService;
+import com.baeldung.concurrent.threadsafety.services.ReentrantLockCounter;
+import com.baeldung.concurrent.threadsafety.services.ReentrantReadWriteLockCounter;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+public class Application {
+    
+    public static void main(String[] args) throws InterruptedException, ExecutionException {
+
+        new Thread(() -> {
+            System.out.println(MathUtils.factorial(10));
+        }).start();
+        new Thread(() -> {
+            System.out.println(MathUtils.factorial(5));
+        }).start();
+        
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+        MessageService messageService = new MessageService("Welcome to Baeldung!");
+        Future<String> future1 = (Future<String>) executorService.submit(new MessageServiceCallable(messageService));
+        Future<String> future2 = (Future<String>) executorService.submit(new MessageServiceCallable(messageService));
+        System.out.println(future1.get());
+        System.out.println(future2.get());
+        
+        Counter counter = new Counter();
+        Future<Integer> future3 = (Future<Integer>) executorService.submit(new CounterCallable(counter));
+        Future<Integer> future4 = (Future<Integer>) executorService.submit(new CounterCallable(counter));
+        System.out.println(future3.get());
+        System.out.println(future4.get());
+        
+        ExtrinsicLockCounter extrinsicLockCounter = new ExtrinsicLockCounter();
+        Future<Integer> future5 = (Future<Integer>) executorService.submit(new ExtrinsicLockCounterCallable(extrinsicLockCounter));
+        Future<Integer> future6 = (Future<Integer>) executorService.submit(new ExtrinsicLockCounterCallable(extrinsicLockCounter));
+        System.out.println(future5.get());
+        System.out.println(future6.get());
+        
+        ReentrantLockCounter reentrantLockCounter = new ReentrantLockCounter();
+        Future<Integer> future7 = (Future<Integer>) executorService.submit(new ReentrantLockCounterCallable(reentrantLockCounter));
+        Future<Integer> future8 = (Future<Integer>) executorService.submit(new ReentrantLockCounterCallable(reentrantLockCounter));
+        System.out.println(future7.get());
+        System.out.println(future8.get());
+        
+        ReentrantReadWriteLockCounter reentrantReadWriteLockCounter = new ReentrantReadWriteLockCounter();
+        Future<Integer> future9 = (Future<Integer>) executorService.submit(new ReentranReadWriteLockCounterCallable(reentrantReadWriteLockCounter));
+        Future<Integer> future10 = (Future<Integer>) executorService.submit(new ReentranReadWriteLockCounterCallable(reentrantReadWriteLockCounter));
+        System.out.println(future9.get());
+        System.out.println(future10.get());
+        
+        AtomicCounter atomicCounter = new AtomicCounter();
+        Future<Integer> future11 = (Future<Integer>) executorService.submit(new AtomicCounterCallable(atomicCounter));
+        Future<Integer> future12 = (Future<Integer>) executorService.submit(new AtomicCounterCallable(atomicCounter));
+        System.out.println(future11.get());
+        System.out.println(future12.get());
+        
+        Collection<Integer> syncCollection = Collections.synchronizedCollection(new ArrayList<>());
+        Thread thread11 = new Thread(() -> syncCollection.addAll(Arrays.asList(1, 2, 3, 4, 5, 6)));
+        Thread thread12 = new Thread(() -> syncCollection.addAll(Arrays.asList(1, 2, 3, 4, 5, 6)));
+        thread11.start();
+        thread12.start();
+        
+        Map<String,String> concurrentMap = new ConcurrentHashMap<>();
+        concurrentMap.put("1", "one");
+        concurrentMap.put("2", "two");
+        concurrentMap.put("3", "three");
+    }
+}
@@ -0,0 +1,19 @@
+package com.baeldung.concurrent.threadsafety.callables;
+
+import com.baeldung.concurrent.threadsafety.services.AtomicCounter;
+import java.util.concurrent.Callable;
+
+public class AtomicCounterCallable implements Callable<Integer> {
+
+    private final AtomicCounter counter;
+    
+    public AtomicCounterCallable(AtomicCounter counter) {
+        this.counter = counter;
+    }
+
+    @Override
+    public Integer call() throws Exception {
+        counter.incrementCounter();
+        return counter.getCounter();
+    }
+}
@@ -0,0 +1,19 @@
+package com.baeldung.concurrent.threadsafety.callables;
+
+import com.baeldung.concurrent.threadsafety.services.Counter;
+import java.util.concurrent.Callable;
+
+public class CounterCallable implements Callable<Integer> {
+
+    private final Counter counter;
+    
+    public CounterCallable(Counter counter) {
+        this.counter = counter;
+    }
+
+    @Override
+    public Integer call() throws Exception {
+        counter.incrementCounter();
+        return counter.getCounter();
+    }
+}
@@ -0,0 +1,19 @@
+package com.baeldung.concurrent.threadsafety.callables;
+
+import com.baeldung.concurrent.threadsafety.services.ExtrinsicLockCounter;
+import java.util.concurrent.Callable;
+
+public class ExtrinsicLockCounterCallable implements Callable<Integer> {
+
+    private final ExtrinsicLockCounter counter;
+    
+    public ExtrinsicLockCounterCallable(ExtrinsicLockCounter counter) {
+        this.counter = counter;
+    }
+    
+    @Override
+    public Integer call() throws Exception {
+        counter.incrementCounter();
+        return counter.getCounter();
+    }
+}
@@ -0,0 +1,19 @@
+package com.baeldung.concurrent.threadsafety.callables;
+
+import com.baeldung.concurrent.threadsafety.services.MessageService;
+import java.util.concurrent.Callable;
+
+public class MessageServiceCallable implements Callable<String> {
+    
+    private final MessageService messageService;
+    
+    public MessageServiceCallable(MessageService messageService) {
+        this.messageService = messageService;
+    
+    }
+    
+    @Override
+    public String call() {
+        return messageService.getMesssage();
+    }
+}
@@ -0,0 +1,20 @@
+package com.baeldung.concurrent.threadsafety.callables;
+
+import com.baeldung.concurrent.threadsafety.services.ReentrantReadWriteLockCounter;
+import java.util.concurrent.Callable;
+
+public class ReentranReadWriteLockCounterCallable implements Callable<Integer> {
+
+    private final ReentrantReadWriteLockCounter counter;
+
+    public ReentranReadWriteLockCounterCallable(ReentrantReadWriteLockCounter counter) {
+        this.counter = counter;
+    }
+    
+    @Override
+    public Integer call() throws Exception {
+        counter.incrementCounter();
+        return counter.getCounter();
+    }
+
+}
@@ -0,0 +1,19 @@
+package com.baeldung.concurrent.threadsafety.callables;
+
+import com.baeldung.concurrent.threadsafety.services.ReentrantLockCounter;
+import java.util.concurrent.Callable;
+
+public class ReentrantLockCounterCallable implements Callable<Integer> {
+
+    private final ReentrantLockCounter counter;
+    
+    public ReentrantLockCounterCallable(ReentrantLockCounter counter) {
+        this.counter = counter;
+    }
+    
+    @Override
+    public Integer call() throws Exception {
+        counter.incrementCounter();
+        return counter.getCounter();
+    }
+}
@@ -0,0 +1,14 @@
+package com.baeldung.concurrent.threadsafety.mathutils;
+
+import java.math.BigInteger;
+
+public class MathUtils {
+    
+    public static BigInteger factorial(int number) {
+        BigInteger f = new BigInteger("1");
+        for (int i = 2; i <= number; i++) {
+            f = f.multiply(BigInteger.valueOf(i));
+        }
+        return f;
+    }
+}
@@ -0,0 +1,18 @@
+package com.baeldung.concurrent.threadsafety.services;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class AtomicCounter {
+    
+    private final AtomicInteger counter = new AtomicInteger();
+    
+    public AtomicCounter() {}
+    
+    public void incrementCounter() {
+        counter.incrementAndGet();
+    }
+    
+    public synchronized int getCounter() {
+        return counter.get();
+    }
+}
@@ -0,0 +1,18 @@
+package com.baeldung.concurrent.threadsafety.services;
+
+public class Counter {
+    
+    private volatile int counter;
+    
+    public Counter() {
+        this.counter = 0;
+    }
+    
+    public synchronized void incrementCounter() {
+        counter += 1;
+    }
+    
+    public int getCounter() {
+        return counter;
+    }
+}
@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.threadsafety.services;
+
+public class ExtrinsicLockCounter {
+
+    private int counter;
+    private final Object lock = new Object();
+
+    public ExtrinsicLockCounter() {
+        this.counter = 0;
+    }
+
+    public void incrementCounter() {
+        synchronized (lock) {
+            counter += 1;
+        }
+    }
+
+    public int getCounter() {
+        synchronized (lock) {
+            return counter;
+        }
+    }
+}
@@ -0,0 +1,14 @@
+package com.baeldung.concurrent.threadsafety.services;
+
+public class MessageService {
+    
+    private final String message;
+    
+    public MessageService(String message) {
+        this.message = message;
+    }
+    
+    public String getMesssage() {
+        return message;
+    }
+}
@@ -0,0 +1,26 @@
+package com.baeldung.concurrent.threadsafety.services;
+
+import java.util.concurrent.locks.ReentrantLock;
+
+public class ReentrantLockCounter {
+
+    private int counter;
+    private final ReentrantLock reLock = new ReentrantLock(true);
+
+    public ReentrantLockCounter() {
+        this.counter = 0;
+    }
+
+    public void incrementCounter() {
+        reLock.lock();
+        try {
+            counter += 1;
+        } finally {
+            reLock.unlock();
+        }
+    }
+
+    public int getCounter() {
+        return counter;
+    }
+}
@@ -0,0 +1,34 @@
+package com.baeldung.concurrent.threadsafety.services;
+
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+
+public class ReentrantReadWriteLockCounter {
+    
+    private int counter;
+    private final ReentrantReadWriteLock rwLock = new ReentrantReadWriteLock();
+    private final Lock readLock = rwLock.readLock();
+    private final Lock writeLock = rwLock.writeLock();
+    
+    public ReentrantReadWriteLockCounter() {
+        this.counter = 0;
+    }
+    
+    public void incrementCounter() {
+        writeLock.lock();
+        try {
+            counter += 1;
+        } finally {
+            writeLock.unlock();
+        }
+    }
+    
+    public int getCounter() {
+        readLock.lock();
+        try {
+            return counter;
+        } finally {
+            readLock.unlock();
+        }
+    }
+}
@@ -0,0 +1,14 @@
+package com.baeldung.concurrent.threadsafety.services;
+
+public class StateHolder {
+    
+    private final String state;
+
+    public StateHolder(String state) {
+        this.state = state;
+    }
+    
+    public String getState() {
+        return state;
+    }
+}
@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.threadsafety.tests;
+
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+import com.baeldung.concurrent.threadsafety.callables.CounterCallable;
+import com.baeldung.concurrent.threadsafety.services.Counter;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+public class CounterTest {
+
+    @Test
+    public void whenCalledIncrementCounter_thenCorrect() throws Exception {
+        ExecutorService executorService = Executors.newFixedThreadPool(2);
+        Counter counter = new Counter();
+        Future<Integer> future1 = (Future<Integer>) executorService.submit(new CounterCallable(counter));
+        Future<Integer> future2 = (Future<Integer>) executorService.submit(new CounterCallable(counter));
+        
+        assertThat(future1.get()).isEqualTo(1);
+        assertThat(future2.get()).isEqualTo(2);
+    }
+}
@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.threadsafety.tests;
+
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+import com.baeldung.concurrent.threadsafety.callables.ExtrinsicLockCounterCallable;
+import com.baeldung.concurrent.threadsafety.services.ExtrinsicLockCounter;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+public class ExtrinsicLockCounterTest {
+
+    @Test
+    public void whenCalledIncrementCounter_thenCorrect() throws Exception {
+        ExecutorService executorService = Executors.newFixedThreadPool(2);
+        ExtrinsicLockCounter counter = new ExtrinsicLockCounter();
+        Future<Integer> future1 = (Future<Integer>) executorService.submit(new ExtrinsicLockCounterCallable(counter));
+        Future<Integer> future2 = (Future<Integer>) executorService.submit(new ExtrinsicLockCounterCallable(counter));
+        
+        assertThat(future1.get()).isEqualTo(1);
+        assertThat(future2.get()).isEqualTo(2);
+    }
+}
@@ -0,0 +1,13 @@
+package com.baeldung.concurrent.threadsafety.tests;
+
+import com.baeldung.concurrent.threadsafety.mathutils.MathUtils;
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class MathUtilsTest {
+    
+    @Test
+    public void whenCalledFactorialMethod_thenCorrect() {
+        assertThat(MathUtils.factorial(2)).isEqualTo(2);
+    }
+}
@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.threadsafety.tests;
+
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+import com.baeldung.concurrent.threadsafety.callables.MessageServiceCallable;
+import com.baeldung.concurrent.threadsafety.services.MessageService;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+public class MessageServiceTest {
+
+    @Test
+    public void whenCalledgetMessage_thenCorrect() throws Exception {
+        ExecutorService executorService = Executors.newFixedThreadPool(2);
+        MessageService messageService = new MessageService("Welcome to Baeldung!");
+        Future<String> future1 = (Future<String>) executorService.submit(new MessageServiceCallable(messageService));
+        Future<String> future2 = (Future<String>) executorService.submit(new MessageServiceCallable(messageService));
+
+        assertThat(future1.get()).isEqualTo("Welcome to Baeldung!");
+        assertThat(future2.get()).isEqualTo("Welcome to Baeldung!");
+    }
+}
@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.threadsafety.tests;
+
+import com.baeldung.concurrent.threadsafety.callables.ReentrantLockCounterCallable;
+import com.baeldung.concurrent.threadsafety.services.ReentrantLockCounter;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.Test;
+
+public class ReentrantLockCounterTest {
+    
+    @Test
+    public void whenCalledIncrementCounter_thenCorrect() throws Exception {
+        ExecutorService executorService = Executors.newFixedThreadPool(2);
+        ReentrantLockCounter counter = new ReentrantLockCounter();
+        Future<Integer> future1 = (Future<Integer>) executorService.submit(new ReentrantLockCounterCallable(counter));
+        Future<Integer> future2 = (Future<Integer>) executorService.submit(new ReentrantLockCounterCallable(counter));
+        
+        assertThat(future1.get()).isEqualTo(1);
+        assertThat(future2.get()).isEqualTo(2);
+    }
+}
@@ -0,0 +1,24 @@
+package com.baeldung.concurrent.threadsafety.tests;
+
+import com.baeldung.concurrent.threadsafety.callables.ReentranReadWriteLockCounterCallable;
+import com.baeldung.concurrent.threadsafety.services.ReentrantReadWriteLockCounter;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.Test;
+
+public class ReentrantReadWriteLockCounterTest {
+    
+    @Test
+    public void whenCalledIncrementCounter_thenCorrect() throws Exception {
+        ExecutorService executorService = Executors.newFixedThreadPool(2);
+        ReentrantReadWriteLockCounter counter = new ReentrantReadWriteLockCounter();
+        Future<Integer> future1 = (Future<Integer>) executorService.submit(new  ReentranReadWriteLockCounterCallable(counter));
+        Future<Integer> future2 = (Future<Integer>) executorService.submit(new  ReentranReadWriteLockCounterCallable(counter));
+        
+        assertThat(future1.get()).isEqualTo(1);
+        assertThat(future2.get()).isEqualTo(2);
+    }
+    
+}
@@ -0,0 +1,60 @@
+package org.baeldung.java.io;
+
+
+import com.google.common.io.ByteStreams;
+import org.apache.commons.io.IOUtils;
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.ReadableByteChannel;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class InputStreamToByteBufferUnitTest {
+
+    @Test
+    public void givenUsingCoreClasses_whenWritingAFileIntoAByteBuffer_thenBytesLengthMustMatch() throws IOException {
+        File inputFile = getFile();
+        ByteBuffer bufferByte = ByteBuffer.allocate((int) inputFile.length());
+        FileInputStream in = new FileInputStream(inputFile);
+        in.getChannel().read(bufferByte);
+
+        assertEquals(bufferByte.position(), inputFile.length());
+    }
+
+    @Test
+    public void givenUsingCommonsIo_whenWritingAFileIntoAByteBuffer_thenBytesLengthMustMatch() throws IOException {
+        File inputFile = getFile();
+        ByteBuffer bufferByte = ByteBuffer.allocateDirect((int) inputFile.length());
+        ReadableByteChannel readableByteChannel = new FileInputStream(inputFile).getChannel();
+        IOUtils.readFully(readableByteChannel, bufferByte);
+
+        assertEquals(bufferByte.position(), inputFile.length());
+    }
+
+    @Test
+    public void givenUsingGuava_whenWritingAFileIntoAByteBuffer_thenBytesLengthMustMatch() throws IOException {
+        File inputFile = getFile();
+        FileInputStream in = new FileInputStream(inputFile);
+        byte[] targetArray = ByteStreams.toByteArray(in);
+        ByteBuffer bufferByte = ByteBuffer.wrap(targetArray);
+        bufferByte.rewind();
+        while (bufferByte.hasRemaining()) {
+            bufferByte.get();
+        }
+        
+        assertEquals(bufferByte.position(), inputFile.length());
+    }
+
+    private File getFile() {
+        ClassLoader classLoader = new InputStreamToByteBufferUnitTest().getClass().getClassLoader();
+
+        String fileName = "frontenac-2257154_960_720.jpg";
+
+        return new File(classLoader.getResource(fileName).getFile());
+    }
+
+}
--- a/Show More
+++ b/Show More