Merge branch 'master' of https://github.com/eugenp/tutorials into task/BAEL-9567

Author: dkapil

core-java-collections/src/main/java/com/baeldung/java/list/WaysToIterate.java

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+package com.baeldung.java.list;
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+import java.util.ListIterator;
+
+/**
+ *  Demonstrates the different ways to loop over
+ *  the elements of a list.
+ */
+public class WaysToIterate {
+
+    List<String> countries = Arrays.asList("Germany", "Panama", "Australia");
+
+    /**
+     * Iterate over a list using a basic for loop
+     */
+    public void iterateWithForLoop() {
+        for (int i = 0; i < countries.size(); i++) {
+            System.out.println(countries.get(i));
+        }
+    }
+
+    /**
+     * Iterate over a list using the enhanced for loop
+     */
+    public void iterateWithEnhancedForLoop() {
+        for (String country : countries) {
+            System.out.println(country);
+        }
+    }
+
+    /**
+     * Iterate over a list using an Iterator
+     */
+    public void iterateWithIterator() {
+        Iterator<String> countriesIterator = countries.iterator();
+        while(countriesIterator.hasNext()) {
+            System.out.println(countriesIterator.next());
+        }
+    }
+
+    /**
+     * Iterate over a list using a ListIterator
+     */
+    public void iterateWithListIterator() {
+        ListIterator<String> listIterator = countries.listIterator();
+        while(listIterator.hasNext()) {
+            System.out.println(listIterator.next());
+        }
+    }
+
+    /**
+     * Iterate over a list using the Iterable.forEach() method
+     */
+    public void iterateWithForEach() {
+        countries.forEach(System.out::println);
+    }
+
+    /**
+     * Iterate over a list using the Stream.forEach() method
+     */
+    public void iterateWithStreamForEach() {
+        countries.stream().forEach((c) -> System.out.println(c));
+    }
+}

core-java-collections/src/test/java/com/baeldung/java/list/WaysToIterateUnitTest.java

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+package com.baeldung.java.list;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
+import java.util.ListIterator;
+
+import org.junit.Test;
+
+public class WaysToIterateUnitTest {
+
+    List<String> globalCountries = new ArrayList<String>();
+    List<String> europeanCountries = Arrays.asList("Germany", "Panama", "Australia");
+
+    @Test
+    public void whenIteratingUsingForLoop_thenReturnThreeAsSizeOfList() {
+        for (int i = 0; i < europeanCountries.size(); i++) {
+            globalCountries.add(europeanCountries.get(i));
+        }
+        assertEquals(globalCountries.size(), 3);
+        globalCountries.clear();
+    }
+
+    @Test
+    public void whenIteratingUsingEnhancedForLoop_thenReturnThreeAsSizeOfList() {
+        for (String country : europeanCountries) {
+            globalCountries.add(country);
+        }
+        assertEquals(globalCountries.size(), 3);
+        globalCountries.clear();
+    }
+
+    @Test
+    public void whenIteratingUsingIterator_thenReturnThreeAsSizeOfList() {
+        Iterator<String> countriesIterator = europeanCountries.iterator();
+        while (countriesIterator.hasNext()) {
+            globalCountries.add(countriesIterator.next());
+        }
+
+        assertEquals(globalCountries.size(), 3);
+        globalCountries.clear();
+    }
+
+    @Test
+    public void whenIteratingUsingListIterator_thenReturnThreeAsSizeOfList() {
+        ListIterator<String> countriesIterator = europeanCountries.listIterator();
+        while (countriesIterator.hasNext()) {
+            globalCountries.add(countriesIterator.next());
+        }
+
+        assertEquals(globalCountries.size(), 3);
+        globalCountries.clear();
+    }
+
+    @Test
+    public void whenIteratingUsingForEach_thenReturnThreeAsSizeOfList() {
+        europeanCountries.forEach(country -> globalCountries.add(country));
+        assertEquals(globalCountries.size(), 3);
+        globalCountries.clear();
+    }
+
+    @Test
+    public void whenIteratingUsingStreamForEach_thenReturnThreeAsSizeOfList() {
+        europeanCountries.stream().forEach((country) -> globalCountries.add(country));
+        assertEquals(globalCountries.size(), 3);
+        globalCountries.clear();
+    }
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/countdownlatch/CountdownLatchCountExample.java

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+package com.baeldung.concurrent.countdownlatch;
+
+import java.util.concurrent.CountDownLatch;
+
+public class CountdownLatchCountExample {
+
+    private int count;
+
+    public CountdownLatchCountExample(int count) {
+        this.count = count;
+    }
+
+    public boolean callTwiceInSameThread() {
+        CountDownLatch countDownLatch = new CountDownLatch(count);
+        Thread t = new Thread(() -> {
+            countDownLatch.countDown();
+            countDownLatch.countDown();
+        });
+        t.start();
+
+        try {
+            countDownLatch.await();
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+        return countDownLatch.getCount() == 0;
+    }
+
+    public static void main(String[] args) {
+        CountdownLatchCountExample ex = new CountdownLatchCountExample(2);
+        System.out.println("Is CountDown Completed : " + ex.callTwiceInSameThread());
+    }
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/countdownlatch/CountdownLatchResetExample.java

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+package com.baeldung.concurrent.countdownlatch;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class CountdownLatchResetExample {
+
+    private int count;
+    private int threadCount;
+    private final AtomicInteger updateCount;
+
+    CountdownLatchResetExample(int count, int threadCount) {
+        updateCount = new AtomicInteger(0);
+        this.count = count;
+        this.threadCount = threadCount;
+    }
+
+    public int countWaits() {
+        CountDownLatch countDownLatch = new CountDownLatch(count);
+        ExecutorService es = Executors.newFixedThreadPool(threadCount);
+        for (int i = 0; i < threadCount; i++) {
+            es.execute(() -> {
+                long prevValue = countDownLatch.getCount();
+                countDownLatch.countDown();
+                if (countDownLatch.getCount() != prevValue) {
+                    updateCount.incrementAndGet();
+                }               
+            });
+        }
+        
+        es.shutdown();
+        return updateCount.get();
+    }
+
+    public static void main(String[] args) {
+        CountdownLatchResetExample ex = new CountdownLatchResetExample(5, 20);
+        System.out.println("Count : " + ex.countWaits());
+    }
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/cyclicbarrier/CyclicBarrierCompletionMethodExample.java

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+package com.baeldung.concurrent.cyclicbarrier;
+
+import java.util.concurrent.BrokenBarrierException;
+import java.util.concurrent.CyclicBarrier;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class CyclicBarrierCompletionMethodExample {
+
+    private int count;
+    private int threadCount;
+    private final AtomicInteger updateCount;
+    
+    CyclicBarrierCompletionMethodExample(int count, int threadCount) {
+        updateCount = new AtomicInteger(0);
+        this.count = count;
+        this.threadCount = threadCount;
+    }
+
+    public int countTrips() {
+
+        CyclicBarrier cyclicBarrier = new CyclicBarrier(count, () -> {
+            updateCount.incrementAndGet();
+        });
+
+        ExecutorService es = Executors.newFixedThreadPool(threadCount);
+        for (int i = 0; i < threadCount; i++) {
+            es.execute(() -> {
+                try {
+                    cyclicBarrier.await();
+                } catch (InterruptedException | BrokenBarrierException e) {
+                    e.printStackTrace();
+                }
+            });
+        }
+        es.shutdown();
+        return updateCount.get();
+    }
+
+    public static void main(String[] args) {
+        CyclicBarrierCompletionMethodExample ex = new CyclicBarrierCompletionMethodExample(5, 20);
+        System.out.println("Count : " + ex.countTrips());
+    }
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/cyclicbarrier/CyclicBarrierCountExample.java

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+package com.baeldung.concurrent.cyclicbarrier;
+
+import java.util.concurrent.BrokenBarrierException;
+import java.util.concurrent.CyclicBarrier;
+
+public class CyclicBarrierCountExample {
+
+    private int count;
+
+    public CyclicBarrierCountExample(int count) {
+        this.count = count;
+    }
+
+    public boolean callTwiceInSameThread() {
+        CyclicBarrier cyclicBarrier = new CyclicBarrier(count);
+        Thread t = new Thread(() -> {
+            try {
+                cyclicBarrier.await();
+                cyclicBarrier.await();
+            } catch (InterruptedException | BrokenBarrierException e) {
+                e.printStackTrace();
+            }
+        });
+        t.start();
+        return cyclicBarrier.isBroken();
+    }
+
+    public static void main(String[] args) {
+        CyclicBarrierCountExample ex = new CyclicBarrierCountExample(7);
+        System.out.println("Count : " + ex.callTwiceInSameThread());
+    }
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/cyclicbarrier/CyclicBarrierResetExample.java

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+package com.baeldung.concurrent.cyclicbarrier;
+
+import java.util.concurrent.BrokenBarrierException;
+import java.util.concurrent.CyclicBarrier;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class CyclicBarrierResetExample {
+
+    private int count;
+    private int threadCount;
+    private final AtomicInteger updateCount;
+
+    CyclicBarrierResetExample(int count, int threadCount) {
+        updateCount = new AtomicInteger(0);
+        this.count = count;
+        this.threadCount = threadCount;
+    }
+
+    public int countWaits() {
+
+        CyclicBarrier cyclicBarrier = new CyclicBarrier(count);
+
+        ExecutorService es = Executors.newFixedThreadPool(threadCount);
+        for (int i = 0; i < threadCount; i++) {
+            es.execute(() -> {
+                try {
+                    if (cyclicBarrier.getNumberWaiting() > 0) {
+                        updateCount.incrementAndGet();
+                    }   
+                    cyclicBarrier.await();
+                } catch (InterruptedException | BrokenBarrierException e) {
+                    e.printStackTrace();
+                }
+            });
+        }
+        es.shutdown();
+        return updateCount.get();
+    }
+
+    public static void main(String[] args) {
+        CyclicBarrierResetExample ex = new CyclicBarrierResetExample(7, 20);
+        System.out.println("Count : " + ex.countWaits());
+    }
+}

core-java-concurrency/src/test/java/com/baeldung/concurrent/countdownlatch/CountdownLatchCountExampleUnitTest.java

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+package com.baeldung.concurrent.countdownlatch;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class CountdownLatchCountExampleUnitTest {
+
+    @Test
+    public void whenCountDownLatch_completed() {
+        CountdownLatchCountExample ex = new CountdownLatchCountExample(2);
+        boolean isCompleted = ex.callTwiceInSameThread();
+        assertTrue(isCompleted);
+    }
+}

core-java-concurrency/src/test/java/com/baeldung/concurrent/countdownlatch/CountdownLatchResetExampleUnitTest.java

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+package com.baeldung.concurrent.countdownlatch;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class CountdownLatchResetExampleUnitTest {
+    
+    @Test
+    public void whenCountDownLatch_noReset() {
+        CountdownLatchResetExample ex = new CountdownLatchResetExample(7,20);
+        int lineCount = ex.countWaits();
+        assertTrue(lineCount <= 7);
+    }
+}

core-java-concurrency/src/test/java/com/baeldung/concurrent/cyclicbarrier/CyclicBarrierCompletionMethodExampleUnitTest.java

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+package com.baeldung.concurrent.cyclicbarrier;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class CyclicBarrierCompletionMethodExampleUnitTest {
+    
+    @Test
+    public void whenCyclicBarrier_countTrips() {
+        CyclicBarrierCompletionMethodExample ex = new CyclicBarrierCompletionMethodExample(7,20);
+        int lineCount = ex.countTrips();
+        assertEquals(2, lineCount);
+    }
+}