Merge remote-tracking branch 'upstream/master'

algorithms/README.md

@@ -15,3 +15,4 @@
 - [Introduction to JGraphT](http://www.baeldung.com/jgrapht)
 - [Introduction to Minimax Algorithm](http://www.baeldung.com/java-minimax-algorithm)
 - [How to Calculate Levenshtein Distance in Java?](http://www.baeldung.com/java-levenshtein-distance)
+- [How to Find the Kth Largest Element in Java](http://www.baeldung.com/java-kth-largest-element)

algorithms/pom.xml

@@ -39,6 +39,12 @@
             <artifactId>jgrapht-core</artifactId>
             <version>1.0.1</version>
         </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>3.9.0</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>

algorithms/src/main/java/com/baeldung/algorithms/kthlargest/FindKthLargest.java

@@ -0,0 +1,111 @@
+package com.baeldung.algorithms.kthlargest;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.stream.IntStream;
+
+public class FindKthLargest {
+
+    public int findKthLargestBySorting(Integer[] arr, int k) {
+        Arrays.sort(arr);
+        int targetIndex = arr.length - k;
+        return arr[targetIndex];
+    }
+
+    public int findKthLargestBySortingDesc(Integer[] arr, int k) {
+        Arrays.sort(arr, Collections.reverseOrder());
+        return arr[k - 1];
+    }
+
+    public int findKthElementByQuickSelect(Integer[] arr, int left, int right, int k) {
+        if (k >= 0 && k <= right - left + 1) {
+            int pos = partition(arr, left, right);
+            if (pos - left == k) {
+                return arr[pos];
+            }
+            if (pos - left > k) {
+                return findKthElementByQuickSelect(arr, left, pos - 1, k);
+            }
+            return findKthElementByQuickSelect(arr, pos + 1, right, k - pos + left - 1);
+        }
+        return 0;
+    }
+
+    public int findKthElementByQuickSelectWithIterativePartition(Integer[] arr, int left, int right, int k) {
+        if (k >= 0 && k <= right - left + 1) {
+            int pos = partitionIterative(arr, left, right);
+            if (pos - left == k) {
+                return arr[pos];
+            }
+            if (pos - left > k) {
+                return findKthElementByQuickSelectWithIterativePartition(arr, left, pos - 1, k);
+            }
+            return findKthElementByQuickSelectWithIterativePartition(arr, pos + 1, right, k - pos + left - 1);
+        }
+        return 0;
+    }
+
+    private int partition(Integer[] arr, int left, int right) {
+        int pivot = arr[right];
+        Integer[] leftArr;
+        Integer[] rightArr;
+
+        leftArr = IntStream.range(left, right)
+            .filter(i -> arr[i] < pivot)
+            .map(i -> arr[i])
+            .boxed()
+            .toArray(Integer[]::new);
+
+        rightArr = IntStream.range(left, right)
+            .filter(i -> arr[i] > pivot)
+            .map(i -> arr[i])
+            .boxed()
+            .toArray(Integer[]::new);
+
+        int leftArraySize = leftArr.length;
+        System.arraycopy(leftArr, 0, arr, left, leftArraySize);
+        arr[leftArraySize + left] = pivot;
+        System.arraycopy(rightArr, 0, arr, left + leftArraySize + 1, rightArr.length);
+
+        return left + leftArraySize;
+    }
+
+    private int partitionIterative(Integer[] arr, int left, int right) {
+        int pivot = arr[right], i = left;
+        for (int j = left; j <= right - 1; j++) {
+            if (arr[j] <= pivot) {
+                swap(arr, i, j);
+                i++;
+            }
+        }
+        swap(arr, i, right);
+        return i;
+    }
+
+    public int findKthElementByRandomizedQuickSelect(Integer[] arr, int left, int right, int k) {
+        if (k >= 0 && k <= right - left + 1) {
+            int pos = randomPartition(arr, left, right);
+            if (pos - left == k) {
+                return arr[pos];
+            }
+            if (pos - left > k) {
+                return findKthElementByRandomizedQuickSelect(arr, left, pos - 1, k);
+            }
+            return findKthElementByRandomizedQuickSelect(arr, pos + 1, right, k - pos + left - 1);
+        }
+        return 0;
+    }
+
+    private int randomPartition(Integer arr[], int left, int right) {
+        int n = right - left + 1;
+        int pivot = (int) (Math.random()) % n;
+        swap(arr, left + pivot, right);
+        return partition(arr, left, right);
+    }
+
+    private void swap(Integer[] arr, int n1, int n2) {
+        int temp = arr[n2];
+        arr[n2] = arr[n1];
+        arr[n1] = temp;
+    }
+}

algorithms/src/test/java/com/baeldung/algorithms/kthlargest/FindKthLargestUnitTest.java

@@ -0,0 +1,57 @@
+package com.baeldung.algorithms.kthlargest;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class FindKthLargestUnitTest {
+
+    private FindKthLargest findKthLargest;
+    private Integer[] arr = { 3, 7, 1, 2, 8, 10, 4, 5, 6, 9 };
+
+    @Before
+    public void setup() {
+        findKthLargest = new FindKthLargest();
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthLargestBySorting_thenGetResult() {
+        int k = 3;
+        assertThat(findKthLargest.findKthLargestBySorting(arr, k)).isEqualTo(8);
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthLargestBySortingDesc_thenGetResult() {
+        int k = 3;
+        assertThat(findKthLargest.findKthLargestBySortingDesc(arr, k)).isEqualTo(8);
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthLargestByQuickSelect_thenGetResult() {
+        int k = 3;
+        int kthLargest = arr.length - k;
+        assertThat(findKthLargest.findKthElementByQuickSelect(arr, 0, arr.length - 1, kthLargest)).isEqualTo(8);
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthElementByQuickSelectIterative_thenGetResult() {
+        int k = 3;
+        int kthLargest = arr.length - k;
+        assertThat(findKthLargest.findKthElementByQuickSelectWithIterativePartition(arr, 0, arr.length - 1, kthLargest)).isEqualTo(8);
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthSmallestByQuickSelect_thenGetResult() {
+        int k = 3;
+        assertThat(findKthLargest.findKthElementByQuickSelect(arr, 0, arr.length - 1, k - 1)).isEqualTo(3);
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthLargestByRandomizedQuickSelect_thenGetResult() {
+        int k = 3;
+        int kthLargest = arr.length - k;
+        assertThat(findKthLargest.findKthElementByRandomizedQuickSelect(arr, 0, arr.length - 1, kthLargest)).isEqualTo(8);
+    }
+
+}

core-java-8/README.md

@@ -34,3 +34,6 @@
 - [Copy a File with Java](http://www.baeldung.com/java-copy-file)
 - [Generating Prime Numbers in Java](http://www.baeldung.com/java-generate-prime-numbers)
 - [Static and Default Methods in Interfaces in Java](http://www.baeldung.com/java-static-default-methods)
+- [Iterable to Stream in Java](http://www.baeldung.com/java-iterable-to-stream)
+- [Converting String to Stream of chars](http://www.baeldung.com/java-string-to-stream)
+- [How to Iterate Over a Stream With Indices](http://www.baeldung.com/java-stream-indices)

core-java-8/pom.xml

@@ -101,6 +101,23 @@
 		    <version>1.19</version>
 		</dependency>
 
+        <dependency>
+            <groupId>com.codepoetics</groupId>
+            <artifactId>protonpack</artifactId>
+            <version>${protonpack.version}</version>
+        </dependency>
+        
+       <dependency>
+            <groupId>io.vavr</groupId>
+            <artifactId>vavr</artifactId>
+            <version>${vavr.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>one.util</groupId>
+            <artifactId>streamex</artifactId>
+            <version>${streamex.version}</version>
+        </dependency>        
     </dependencies>
 
     <build>
@@ -267,6 +284,9 @@
         <collections-generic.version>4.01</collections-generic.version>
         <commons-codec.version>1.10</commons-codec.version>
         <lombok.version>1.16.12</lombok.version>
+        <vavr.version>0.9.0</vavr.version>
+        <protonpack.version>1.13</protonpack.version>
+        <streamex.version>0.6.5</streamex.version>
 
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>

core-java-8/src/main/java/com/baeldung/spliteratorAPI/Article.java

@@ -0,0 +1,44 @@
+package com.baeldung.spliteratorAPI;
+
+import java.util.List;
+
+public class Article {
+    private List<Author> listOfAuthors;
+    private int id;
+    private String name;
+
+    public Article(String name) {
+        this.name = name;
+    }
+
+    public Article(List<Author> listOfAuthors, int id) {
+        super();
+        this.listOfAuthors = listOfAuthors;
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public List<Author> getListOfAuthors() {
+        return listOfAuthors;
+    }
+
+    public void setListOfAuthors(List<Author> listOfAuthors) {
+        this.listOfAuthors = listOfAuthors;
+    }
+
+}

core-java-8/src/main/java/com/baeldung/spliteratorAPI/Author.java

@@ -0,0 +1,33 @@
+package com.baeldung.spliteratorAPI;
+
+public class Author {
+    private String name;
+    private int relatedArticleId;
+
+    public Author(String name, int relatedArticleId) {
+        this.name = name;
+        this.relatedArticleId = relatedArticleId;
+    }
+
+    public int getRelatedArticleId() {
+        return relatedArticleId;
+    }
+
+    public void setRelatedArticleId(int relatedArticleId) {
+        this.relatedArticleId = relatedArticleId;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public String toString() {
+        return "[name: " + name + ", relatedId: " + relatedArticleId + "]";
+    }
+}
+

core-java-8/src/main/java/com/baeldung/spliteratorAPI/Executor.java

@@ -0,0 +1,45 @@
+package com.baeldung.spliteratorAPI;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Spliterator;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+public class Executor {
+	public void executeCustomSpliterator() {
+        Article article = new Article(Arrays.asList(new Author("Ahmad", 0), new Author("Eugen", 0), new Author("Alice", 1), new Author("Alice", 1), new Author("Mike", 0), new Author("Alice", 1), new Author("Mike", 0), new Author("Alice", 1),
+            new Author("Mike", 0), new Author("Alice", 1), new Author("Mike", 0), new Author("Mike", 0), new Author("Alice", 1), new Author("Mike", 0), new Author("Alice", 1), new Author("Mike", 0), new Author("Alice", 1), new Author("Mike", 0),
+            new Author("Alice", 1), new Author("Mike", 0), new Author("Michał", 0), new Author("Loredana", 1)), 0);
+        Stream<Author> stream = IntStream.range(0, article.getListOfAuthors()
+            .size())
+            .mapToObj(article.getListOfAuthors()::get);
+        System.out.println("count= " + countAutors(stream.parallel()));
+        Spliterator<Author> spliterator = new RelatedAuthorSpliterator(article.getListOfAuthors());
+        Stream<Author> stream2 = StreamSupport.stream(spliterator, true);
+        System.out.println("count= " + countAutors(stream2.parallel()));
+    }
+
+    public void executeSpliterator() {
+        Spliterator<Article> split1 = generateElements().spliterator();
+        Spliterator<Article> split2 = split1.trySplit();
+        ExecutorService service = Executors.newCachedThreadPool();
+        service.execute(new Task(split1));
+        service.execute(new Task(split2));
+    }
+
+    private static int countAutors(Stream<Author> stream) {
+        RelatedAuthorCounter wordCounter = stream.reduce(new RelatedAuthorCounter(0, true), RelatedAuthorCounter::accumulate, RelatedAuthorCounter::combine);
+        return wordCounter.getCounter();
+    }
+
+    private List<Article> generateElements() {
+        return Stream.generate(() -> new Article("Java"))
+            .limit(35000)
+            .collect(Collectors.toList());
+    }
+}

core-java-8/src/main/java/com/baeldung/spliteratorAPI/RelatedAuthorCounter.java

@@ -0,0 +1,27 @@
+package com.baeldung.spliteratorAPI;
+
+public class RelatedAuthorCounter {
+    private final int counter;
+    private final boolean isRelated;
+
+    public RelatedAuthorCounter(int counter, boolean isRelated) {
+        this.counter = counter;
+        this.isRelated = isRelated;
+    }
+
+    public RelatedAuthorCounter accumulate(Author author) {
+        if (author.getRelatedArticleId() == 0) {
+            return isRelated ? this : new RelatedAuthorCounter(counter, true);
+        } else {
+            return isRelated ? new RelatedAuthorCounter(counter + 1, false) : this;
+        }
+    }
+
+    public RelatedAuthorCounter combine(RelatedAuthorCounter RelatedAuthorCounter) {
+        return new RelatedAuthorCounter(counter + RelatedAuthorCounter.counter, RelatedAuthorCounter.isRelated);
+    }
+
+    public int getCounter() {
+        return counter;
+    }
+}

core-java-8/src/main/java/com/baeldung/spliteratorAPI/RelatedAuthorSpliterator.java

@@ -0,0 +1,47 @@
+package com.baeldung.spliteratorAPI;
+
+import java.util.List;
+import java.util.Spliterator;
+import java.util.function.Consumer;
+
+public class RelatedAuthorSpliterator implements Spliterator<Author> {
+    private final List<Author> list;
+    private int current = 0;
+
+    public RelatedAuthorSpliterator(List<Author> list) {
+        this.list = list;
+    }
+
+    @Override
+    public boolean tryAdvance(Consumer<? super Author> action) {
+        action.accept(list.get(current++));
+        return current < list.size();
+    }
+
+    @Override
+    public Spliterator<Author> trySplit() {
+        int currentSize = list.size() - current;
+        if (currentSize < 10) {
+            return null;
+        }
+        for (int splitPos = currentSize / 2 + current; splitPos < list.size(); splitPos++) {
+            if (list.get(splitPos)
+                .getRelatedArticleId() == 0) {
+                Spliterator<Author> spliterator = new RelatedAuthorSpliterator(list.subList(current, splitPos));
+                current = splitPos;
+                return spliterator;
+            }
+        }
+        return null;
+    }
+
+    @Override
+    public long estimateSize() {
+        return list.size() - current;
+    }
+
+    @Override
+    public int characteristics() {
+        return SIZED + CONCURRENT;
+    }
+}

core-java-8/src/main/java/com/baeldung/spliteratorAPI/Task.java

@@ -0,0 +1,26 @@
+package com.baeldung.spliteratorAPI;
+
+import java.util.Spliterator;
+
+public class Task implements Runnable {
+    private Spliterator<Article> spliterator;
+    private final static String SUFFIX = "- published by Baeldung";
+
+    public Task(Spliterator<Article> spliterator) {
+        this.spliterator = spliterator;
+    }
+
+    @Override
+    public void run() {
+        int current = 0;
+        while (spliterator.tryAdvance(article -> {
+            article.setName(article.getName()
+                .concat(SUFFIX));
+        })) {
+            current++;
+        }
+        ;
+        System.out.println(Thread.currentThread()
+            .getName() + ":" + current);
+    }
+}

core-java-concurrency/src/main/java/com/baeldung/concurrent/stopping/ControlSubThread.java

@@ -43,8 +43,9 @@ public class ControlSubThread implements Runnable {
             try {
                 Thread.sleep(interval);
             } catch (InterruptedException e) {
-                // no-op, just loop again
-            }
+            	Thread.currentThread().interrupt();
+                System.out.println("Thread was interrupted, Failed to complete operation");
+	    }
             // do something
         }
         stopped.set(true);

core-java-concurrency/src/test/java/com/baeldung/concurrent/stopping/StopThreadTest.java

@@ -1,20 +1,21 @@
 package com.baeldung.concurrent.stopping;
 
-import com.jayway.awaitility.Awaitility;
-import org.junit.Test;
-
-import java.util.concurrent.TimeUnit;
-
 import static com.jayway.awaitility.Awaitility.await;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
+import java.util.concurrent.TimeUnit;
+
+import org.junit.Test;
+
+import com.jayway.awaitility.Awaitility;
+
 public class StopThreadTest {
 
     @Test
     public void whenStoppedThreadIsStopped() throws InterruptedException {
 
-        int interval = 100;
+        int interval = 5;
 
         ControlSubThread controlSubThread = new ControlSubThread(interval);
         controlSubThread.start();
@@ -33,13 +34,13 @@ public class StopThreadTest {
     @Test
     public void whenInterruptedThreadIsStopped() throws InterruptedException {
 
-        int interval = 5000;
+        int interval = 50;
 
         ControlSubThread controlSubThread = new ControlSubThread(interval);
         controlSubThread.start();
 
         // Give things a chance to get set up
-        Thread.sleep(100);
+        Thread.sleep(interval);
         assertTrue(controlSubThread.isRunning());
         assertFalse(controlSubThread.isStopped());
 
@@ -48,6 +49,7 @@ public class StopThreadTest {
 
         // Wait less than the time we would normally sleep, and make sure we exited.
         Awaitility.await()
+            .pollDelay(2, TimeUnit.MILLISECONDS)
           .atMost(interval/ 10, TimeUnit.MILLISECONDS)
           .until(controlSubThread::isStopped);
     }

core-java-io/.gitignore

@@ -0,0 +1,26 @@
+*.class
+
+0.*
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+.resourceCache
+
+# Packaged files #
+*.jar
+*.war
+*.ear
+
+# Files generated by integration tests
+*.txt
+backup-pom.xml
+/bin/
+/temp
+
+#IntelliJ specific
+.idea/
+*.iml

core-java-io/README.md

@@ -0,0 +1,25 @@
+=========
+
+## Core Java IO Cookbooks and Examples
+
+### Relevant Articles: 
+- [Java - Reading a Large File Efficiently](http://www.baeldung.com/java-read-lines-large-file)
+- [Java InputStream to String](http://www.baeldung.com/convert-input-stream-to-string)
+- [Java – Write to File](http://www.baeldung.com/java-write-to-file)
+- [Java - Convert File to InputStream](http://www.baeldung.com/convert-file-to-input-stream)
+- [Java Scanner](http://www.baeldung.com/java-scanner)
+- [Java – Byte Array to Writer](http://www.baeldung.com/java-convert-byte-array-to-writer)
+- [Java – Directory Size](http://www.baeldung.com/java-folder-size)
+- [Differences Between the Java WatchService API and the Apache Commons IO Monitor Library](http://www.baeldung.com/java-watchservice-vs-apache-commons-io-monitor-library)
+- [Calculate the Size of a File in Java](http://www.baeldung.com/java-file-size)
+- [Comparing getPath(), getAbsolutePath(), and getCanonicalPath() in Java](http://www.baeldung.com/java-path)
+- [Using Java MappedByteBuffer](http://www.baeldung.com/java-mapped-byte-buffer)
+- [Copy a File with Java](http://www.baeldung.com/java-copy-file)
+- [Java – Append Data to a File](http://www.baeldung.com/java-append-to-file)
+- [FileNotFoundException in Java](http://www.baeldung.com/java-filenotfound-exception)
+- [How to Read a File in Java](http://www.baeldung.com/reading-file-in-java)
+- [A Guide To NIO2 Asynchronous File Channel](http://www.baeldung.com/java-nio2-async-file-channel)
+- [A Guide To NIO2 FileVisitor](http://www.baeldung.com/java-nio2-file-visitor)
+- [A Guide To NIO2 File Attribute APIs](http://www.baeldung.com/java-nio2-file-attribute)
+- [Introduction to the Java NIO2 File API](http://www.baeldung.com/java-nio-2-file-api)
+- [Zipping and Unzipping in Java](http://www.baeldung.com/java-compress-and-uncompress)

core-java-io/src/main/java/com/baeldung/filesystem/jndi/LookupFSJNDI.java

@@ -0,0 +1,42 @@
+package com.baeldung.filesystem.jndi;
+
+import java.io.File;
+import java.util.Hashtable;
+
+import javax.naming.Context;
+import javax.naming.InitialContext;
+import javax.naming.NamingException;
+
+public class LookupFSJNDI {
+    private InitialContext ctx = null;
+
+    public LookupFSJNDI() throws NamingException {
+        super();
+        init();
+    }
+
+    private void init() throws NamingException {
+        Hashtable<String, String> env = new Hashtable<String, String>();
+
+        env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.fscontext.RefFSContextFactory");
+        // URI to namespace (actual directory)
+        env.put(Context.PROVIDER_URL, "file:./src/test/resources");
+
+        ctx = new InitialContext(env);
+    }
+
+    public InitialContext getCtx() {
+        return ctx;
+    }
+
+    public File getFile(String fileName) {
+        File file;
+        try {
+            file = (File) getCtx().lookup(fileName);
+        } catch (NamingException e) {
+            file = null;
+        }
+        return file;
+    }
+
+}