Merge remote-tracking branch 'eugenp/master'

2017-09-20 13:35:33 +02:00
parent 8c43cc2bb6 60acc2fd1d
commit 8aa9a65548
480 changed files with 17025 additions and 1299 deletions
@@ -41,3 +41,5 @@ SpringDataInjectionDemo/.mvn/wrapper/maven-wrapper.properties
 spring-call-getters-using-reflection/.mvn/wrapper/maven-wrapper.properties

 spring-check-if-a-property-is-null/.mvn/wrapper/maven-wrapper.properties
+*.springBeans
+
@@ -23,4 +23,4 @@ Any IDE can be used to work with the projects, but if you're using Eclipse, cons

 CI - Jenkins
 ================================
-This tutorials project is being built **[>> HERE](https://rest-security.ci.cloudbees.com/job/tutorials/)**
+This tutorials project is being built **[>> HERE](https://rest-security.ci.cloudbees.com/job/github%20projects%20Jobs/job/tutorials/)**
@@ -8,3 +8,4 @@
 - [Check If a Number Is Prime in Java](http://www.baeldung.com/java-prime-numbers)
 - [Example of Hill Climbing Algorithm](http://www.baeldung.com/java-hill-climbing-algorithm)
 - [Monte Carlo Tree Search for Tic-Tac-Toe Game](http://www.baeldung.com/java-monte-carlo-tree-search)
+- [String Search Algorithms for Large Texts](http://www.baeldung.com/java-full-text-search-algorithms)
@@ -1,3 +1,5 @@
+package com.baeldung.algorithms.binarysearch;
+
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
@@ -0,0 +1,38 @@
+package com.baeldung.algorithms.linkedlist;
+
+public class CycleDetectionBruteForce {
+
+    public static <T> CycleDetectionResult<T> detectCycle(Node<T> head) {
+        if (head == null) {
+            return new CycleDetectionResult<>(false, null);
+        }
+
+        Node<T> it1 = head;
+        int nodesTraversedByOuter = 0;
+        while (it1 != null && it1.next != null) {
+            it1 = it1.next;
+            nodesTraversedByOuter++;
+
+            int x = nodesTraversedByOuter;
+            Node<T> it2 = head;
+            int noOfTimesCurrentNodeVisited = 0;
+
+            while (x > 0) {
+                it2 = it2.next;
+
+                if (it2 == it1) {
+                    noOfTimesCurrentNodeVisited++;
+                }
+
+                if (noOfTimesCurrentNodeVisited == 2) {
+                    return new CycleDetectionResult<>(true, it1);
+                }
+
+                x--;
+            }
+        }
+
+        return new CycleDetectionResult<>(false, null);
+    }
+
+}
@@ -0,0 +1,25 @@
+package com.baeldung.algorithms.linkedlist;
+
+public class CycleDetectionByFastAndSlowIterators {
+
+    public static <T> CycleDetectionResult<T> detectCycle(Node<T> head) {
+        if (head == null) {
+            return new CycleDetectionResult<>(false, null);
+        }
+
+        Node<T> slow = head;
+        Node<T> fast = head;
+
+        while (fast != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+
+            if (slow == fast) {
+                return new CycleDetectionResult<>(true, fast);
+            }
+        }
+
+        return new CycleDetectionResult<>(false, null);
+    }
+
+}
@@ -0,0 +1,27 @@
+package com.baeldung.algorithms.linkedlist;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class CycleDetectionByHashing {
+
+    public static <T> CycleDetectionResult<T> detectCycle(Node<T> head) {
+        if (head == null) {
+            return new CycleDetectionResult<>(false, null);
+        }
+
+        Set<Node<T>> set = new HashSet<>();
+        Node<T> node = head;
+
+        while (node != null) {
+            if (set.contains(node)) {
+                return new CycleDetectionResult<>(true, node);
+            }
+            set.add(node);
+            node = node.next;
+        }
+
+        return new CycleDetectionResult<>(false, null);
+    }
+
+}
@@ -0,0 +1,12 @@
+package com.baeldung.algorithms.linkedlist;
+
+public class CycleDetectionResult<T> {
+    boolean cycleExists;
+    Node<T> node;
+
+    public CycleDetectionResult(boolean cycleExists, Node<T> node) {
+        super();
+        this.cycleExists = cycleExists;
+        this.node = node;
+    }
+}
@@ -0,0 +1,56 @@
+package com.baeldung.algorithms.linkedlist;
+
+public class CycleRemovalBruteForce {
+
+    public static <T> boolean detectAndRemoveCycle(Node<T> head) {
+        CycleDetectionResult<T> result = CycleDetectionByFastAndSlowIterators.detectCycle(head);
+
+        if (result.cycleExists) {
+            removeCycle(result.node, head);
+        }
+
+        return result.cycleExists;
+    }
+
+    /**
+     * @param loopNodeParam - reference to the node where Flyods cycle 
+     * finding algorithm ends, i.e. the fast and the slow iterators
+     * meet.
+     * @param head - reference to the head of the list
+     */
+    private static <T> void removeCycle(Node<T> loopNodeParam, Node<T> head) {
+        Node<T> it = head;
+
+        while (it != null) {
+            if (isNodeReachableFromLoopNode(it, loopNodeParam)) {
+                Node<T> loopStart = it;
+                findEndNodeAndBreakCycle(loopStart);
+                break;
+            }
+            it = it.next;
+        }
+    }
+
+    private static <T> boolean isNodeReachableFromLoopNode(Node<T> it, Node<T> loopNodeParam) {
+        Node<T> loopNode = loopNodeParam;
+
+        do {
+            if (it == loopNode) {
+                return true;
+            }
+            loopNode = loopNode.next;
+        } while (loopNode.next != loopNodeParam);
+
+        return false;
+    }
+
+    private static <T> void findEndNodeAndBreakCycle(Node<T> loopStartParam) {
+        Node<T> loopStart = loopStartParam;
+
+        while (loopStart.next != loopStartParam) {
+            loopStart = loopStart.next;
+        }
+
+        loopStart.next = null;
+    }
+}
@@ -0,0 +1,44 @@
+package com.baeldung.algorithms.linkedlist;
+
+public class CycleRemovalByCountingLoopNodes {
+
+    public static <T> boolean detectAndRemoveCycle(Node<T> head) {
+        CycleDetectionResult<T> result = CycleDetectionByFastAndSlowIterators.detectCycle(head);
+
+        if (result.cycleExists) {
+            removeCycle(result.node, head);
+        }
+
+        return result.cycleExists;
+    }
+
+    private static <T> void removeCycle(Node<T> loopNodeParam, Node<T> head) {
+        int cycleLength = calculateCycleLength(loopNodeParam);
+        Node<T> cycleLengthAdvancedIterator = head;
+        Node<T> it = head;
+
+        for (int i = 0; i < cycleLength; i++) {
+            cycleLengthAdvancedIterator = cycleLengthAdvancedIterator.next;
+        }
+
+        while (it.next != cycleLengthAdvancedIterator.next) {
+            it = it.next;
+            cycleLengthAdvancedIterator = cycleLengthAdvancedIterator.next;
+        }
+
+        cycleLengthAdvancedIterator.next = null;
+    }
+
+    private static <T> int calculateCycleLength(Node<T> loopNodeParam) {
+        Node<T> loopNode = loopNodeParam;
+        int length = 1;
+
+        while (loopNode.next != loopNodeParam) {
+            length++;
+            loopNode = loopNode.next;
+        }
+
+        return length;
+    }
+
+}
@@ -0,0 +1,27 @@
+package com.baeldung.algorithms.linkedlist;
+
+public class CycleRemovalWithoutCountingLoopNodes {
+
+    public static <T> boolean detectAndRemoveCycle(Node<T> head) {
+        CycleDetectionResult<T> result = CycleDetectionByFastAndSlowIterators.detectCycle(head);
+
+        if (result.cycleExists) {
+            removeCycle(result.node, head);
+        }
+
+        return result.cycleExists;
+    }
+
+    private static <T> void removeCycle(Node<T> meetingPointParam, Node<T> head) {
+        Node<T> loopNode = meetingPointParam;
+        Node<T> it = head;
+
+        while (loopNode.next != it.next) {
+            it = it.next;
+            loopNode = loopNode.next;
+        }
+
+        loopNode.next = null;
+    }
+
+}
@@ -0,0 +1,38 @@
+package com.baeldung.algorithms.linkedlist;
+
+public class Node<T> {
+    T data;
+    Node<T> next;
+
+    public static <T> Node<T> createNewNode(T data, Node<T> next) {
+        Node<T> node = new Node<T>();
+        node.data = data;
+        node.next = next;
+        return node;
+    }
+
+    public static <T> void traverseList(Node<T> root) {
+        if (root == null) {
+            return;
+        }
+
+        Node<T> node = root;
+        while (node != null) {
+            System.out.println(node.data);
+            node = node.next;
+        }
+    }
+
+    public static <T> Node<T> getTail(Node<T> root) {
+        if (root == null) {
+            return null;
+        }
+
+        Node<T> node = root;
+        while (node.next != null) {
+            node = node.next;
+        }
+        return node;
+    }
+
+}
@@ -0,0 +1,194 @@
+package com.baeldung.algorithms.string.search;
+
+import java.math.BigInteger;
+import java.util.Random;
+
+public class StringSearchAlgorithms {
+    public static long getBiggerPrime(int m) {
+        BigInteger prime = BigInteger.probablePrime(getNumberOfBits(m) + 1, new Random());
+        return prime.longValue();
+    }
+
+    public static long getLowerPrime(long number) {
+        BigInteger prime = BigInteger.probablePrime(getNumberOfBits(number) - 1, new Random());
+        return prime.longValue();
+    }
+
+    private static int getNumberOfBits(final int number) {
+        return Integer.SIZE - Integer.numberOfLeadingZeros(number);
+    }
+
+    private static int getNumberOfBits(final long number) {
+        return Long.SIZE - Long.numberOfLeadingZeros(number);
+    }
+
+    public static int simpleTextSearch(char[] pattern, char[] text) {
+        int patternSize = pattern.length;
+        int textSize = text.length;
+
+        int i = 0;
+
+        while ((i + patternSize) <= textSize) {
+            int j = 0;
+            while (text[i + j] == pattern[j]) {
+                j += 1;
+                if (j >= patternSize)
+                    return i;
+            }
+            i += 1;
+        }
+
+        return -1;
+    }
+
+    public static int RabinKarpMethod(char[] pattern, char[] text) {
+        int patternSize = pattern.length; // m
+        int textSize = text.length; // n
+
+        long prime = getBiggerPrime(patternSize);
+
+        long r = 1;
+        for (int i = 0; i < patternSize - 1; i++) {
+            r *= 2;
+            r = r % prime;
+        }
+
+        long[] t = new long[textSize];
+        t[0] = 0;
+
+        long pfinger = 0;
+
+        for (int j = 0; j < patternSize; j++) {
+            t[0] = (2 * t[0] + text[j]) % prime;
+            pfinger = (2 * pfinger + pattern[j]) % prime;
+        }
+
+        int i = 0;
+        boolean passed = false;
+
+        int diff = textSize - patternSize;
+        for (i = 0; i <= diff; i++) {
+            if (t[i] == pfinger) {
+                passed = true;
+                for (int k = 0; k < patternSize; k++) {
+                    if (text[i + k] != pattern[k]) {
+                        passed = false;
+                        break;
+                    }
+                }
+
+                if (passed) {
+                    return i;
+                }
+            }
+
+            if (i < diff) {
+                long value = 2 * (t[i] - r * text[i]) + text[i + patternSize];
+                t[i + 1] = ((value % prime) + prime) % prime;
+            }
+        }
+        return -1;
+
+    }
+
+    public static int KnuthMorrisPrattSearch(char[] pattern, char[] text) {
+        int patternSize = pattern.length; // m
+        int textSize = text.length; // n
+
+        int i = 0, j = 0;
+
+        int[] shift = KnuthMorrisPrattShift(pattern);
+
+        while ((i + patternSize) <= textSize) {
+            while (text[i + j] == pattern[j]) {
+                j += 1;
+                if (j >= patternSize)
+                    return i;
+            }
+
+            if (j > 0) {
+                i += shift[j - 1];
+                j = Math.max(j - shift[j - 1], 0);
+            } else {
+                i++;
+                j = 0;
+            }
+        }
+        return -1;
+    }
+
+    public static int[] KnuthMorrisPrattShift(char[] pattern) {
+        int patternSize = pattern.length;
+
+        int[] shift = new int[patternSize];
+        shift[0] = 1;
+
+        int i = 1, j = 0;
+
+        while ((i + j) < patternSize) {
+            if (pattern[i + j] == pattern[j]) {
+                shift[i + j] = i;
+                j++;
+            } else {
+                if (j == 0)
+                    shift[i] = i + 1;
+
+                if (j > 0) {
+                    i = i + shift[j - 1];
+                    j = Math.max(j - shift[j - 1], 0);
+                } else {
+                    i = i + 1;
+                    j = 0;
+                }
+            }
+        }
+        return shift;
+    }
+
+    public static int BoyerMooreHorspoolSimpleSearch(char[] pattern, char[] text) {
+        int patternSize = pattern.length;
+        int textSize = text.length;
+
+        int i = 0, j = 0;
+
+        while ((i + patternSize) <= textSize) {
+            j = patternSize - 1;
+            while (text[i + j] == pattern[j]) {
+                j--;
+                if (j < 0)
+                    return i;
+            }
+            i++;
+        }
+        return -1;
+    }
+
+    public static int BoyerMooreHorspoolSearch(char[] pattern, char[] text) {
+
+        int shift[] = new int[256];
+
+        for (int k = 0; k < 256; k++) {
+            shift[k] = pattern.length;
+        }
+
+        for (int k = 0; k < pattern.length - 1; k++) {
+            shift[pattern[k]] = pattern.length - 1 - k;
+        }
+
+        int i = 0, j = 0;
+
+        while ((i + pattern.length) <= text.length) {
+            j = pattern.length - 1;
+
+            while (text[i + j] == pattern[j]) {
+                j -= 1;
+                if (j < 0)
+                    return i;
+            }
+
+            i = i + shift[text[i + pattern.length - 1]];
+
+        }
+        return -1;
+    }
+}
@@ -0,0 +1,25 @@
+package algorithms;
+
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import com.baeldung.algorithms.string.search.StringSearchAlgorithms;
+
+public class StringSearchAlgorithmsTest {
+	
+	
+	@Test
+	public void testStringSearchAlgorithms(){
+		String text = "This is some nice text.";
+		String pattern = "some";
+		
+		int realPosition = text.indexOf(pattern);
+        Assert.assertTrue(realPosition == StringSearchAlgorithms.simpleTextSearch(pattern.toCharArray(), text.toCharArray()));
+        Assert.assertTrue(realPosition == StringSearchAlgorithms.RabinKarpMethod(pattern.toCharArray(), text.toCharArray()));
+        Assert.assertTrue(realPosition == StringSearchAlgorithms.KnuthMorrisPrattSearch(pattern.toCharArray(), text.toCharArray()));
+        Assert.assertTrue(realPosition == StringSearchAlgorithms.BoyerMooreHorspoolSimpleSearch(pattern.toCharArray(), text.toCharArray()));
+        Assert.assertTrue(realPosition == StringSearchAlgorithms.BoyerMooreHorspoolSearch(pattern.toCharArray(), text.toCharArray()));
+	}
+
+}
@@ -1,9 +1,11 @@
+package algorithms.binarysearch;
+
 import java.util.Arrays;
 import java.util.List;

 import org.junit.Assert;
 import org.junit.Test;
-
+import com.baeldung.algorithms.binarysearch.BinarySearch;

 public class BinarySearchTest {

@@ -0,0 +1,23 @@
+package com.baeldung.algorithms.linkedlist;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+@RunWith(value = Parameterized.class)
+public class CycleDetectionBruteForceTest extends CycleDetectionTestBase {
+    boolean cycleExists;
+    Node<Integer> head;
+
+    public CycleDetectionBruteForceTest(Node<Integer> head, boolean cycleExists) {
+        super();
+        this.cycleExists = cycleExists;
+        this.head = head;
+    }
+
+    @Test
+    public void givenList_detectLoop() {
+        Assert.assertEquals(cycleExists, CycleDetectionBruteForce.detectCycle(head).cycleExists);
+    }
+}
@@ -0,0 +1,23 @@
+package com.baeldung.algorithms.linkedlist;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+@RunWith(value = Parameterized.class)
+public class CycleDetectionByFastAndSlowIteratorsTest extends CycleDetectionTestBase {
+    boolean cycleExists;
+    Node<Integer> head;
+
+    public CycleDetectionByFastAndSlowIteratorsTest(Node<Integer> head, boolean cycleExists) {
+        super();
+        this.cycleExists = cycleExists;
+        this.head = head;
+    }
+
+    @Test
+    public void givenList_detectLoop() {
+        Assert.assertEquals(cycleExists, CycleDetectionByFastAndSlowIterators.detectCycle(head).cycleExists);
+    }
+}
@@ -0,0 +1,23 @@
+package com.baeldung.algorithms.linkedlist;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+@RunWith(value = Parameterized.class)
+public class CycleDetectionByHashingTest extends CycleDetectionTestBase {
+    boolean cycleExists;
+    Node<Integer> head;
+
+    public CycleDetectionByHashingTest(Node<Integer> head, boolean cycleExists) {
+        super();
+        this.cycleExists = cycleExists;
+        this.head = head;
+    }
+
+    @Test
+    public void givenList_detectLoop() {
+        Assert.assertEquals(cycleExists, CycleDetectionByHashing.detectCycle(head).cycleExists);
+    }
+}
@@ -0,0 +1,62 @@
+package com.baeldung.algorithms.linkedlist;
+
+import java.util.Arrays;
+import java.util.Collection;
+
+import org.junit.runners.Parameterized.Parameters;
+
+public class CycleDetectionTestBase {
+
+    @Parameters
+    public static Collection<Object[]> getLists() {
+        return Arrays.asList(new Object[][] { 
+            { createList(), false }, 
+            { createListWithLoop(), true },
+            { createListWithFullCycle(), true }, 
+            { createListWithSingleNodeInCycle(), true } 
+        });
+    }
+
+    public static Node<Integer> createList() {
+        Node<Integer> root = Node.createNewNode(10, null);
+
+        for (int i = 9; i >= 1; --i) {
+            Node<Integer> current = Node.createNewNode(i, root);
+            root = current;
+        }
+
+        return root;
+    }
+
+    public static Node<Integer> createListWithLoop() {
+        Node<Integer> node = createList();
+        createLoop(node);
+        return node;
+    }
+
+    public static Node<Integer> createListWithFullCycle() {
+        Node<Integer> head = createList();
+        Node<Integer> tail = Node.getTail(head);
+        tail.next = head;
+        return head;
+    }
+
+    public static Node<Integer> createListWithSingleNodeInCycle() {
+        Node<Integer> head = createList();
+        Node<Integer> tail = Node.getTail(head);
+        tail.next = tail;
+        return head;
+    }
+
+    public static void createLoop(Node<Integer> root) {
+        Node<Integer> tail = Node.getTail(root);
+
+        Node<Integer> middle = root;
+        for (int i = 1; i <= 4; i++) {
+            middle = middle.next;
+        }
+
+        tail.next = middle;
+    }
+
+}
@@ -0,0 +1,24 @@
+package com.baeldung.algorithms.linkedlist;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+@RunWith(value = Parameterized.class)
+public class CycleRemovalBruteForceTest extends CycleDetectionTestBase {
+    boolean cycleExists;
+    Node<Integer> head;
+
+    public CycleRemovalBruteForceTest(Node<Integer> head, boolean cycleExists) {
+        super();
+        this.cycleExists = cycleExists;
+        this.head = head;
+    }
+
+    @Test
+    public void givenList_ifLoopExists_thenDetectAndRemoveLoop() {
+        Assert.assertEquals(cycleExists, CycleRemovalBruteForce.detectAndRemoveCycle(head));
+        Assert.assertFalse(CycleDetectionByFastAndSlowIterators.detectCycle(head).cycleExists);
+    }
+}
@@ -0,0 +1,24 @@
+package com.baeldung.algorithms.linkedlist;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+@RunWith(value = Parameterized.class)
+public class CycleRemovalByCountingLoopNodesTest extends CycleDetectionTestBase {
+    boolean cycleExists;
+    Node<Integer> head;
+
+    public CycleRemovalByCountingLoopNodesTest(Node<Integer> head, boolean cycleExists) {
+        super();
+        this.cycleExists = cycleExists;
+        this.head = head;
+    }
+
+    @Test
+    public void givenList_ifLoopExists_thenDetectAndRemoveLoop() {
+        Assert.assertEquals(cycleExists, CycleRemovalByCountingLoopNodes.detectAndRemoveCycle(head));
+        Assert.assertFalse(CycleDetectionByFastAndSlowIterators.detectCycle(head).cycleExists);
+    }
+}
@@ -0,0 +1,24 @@
+package com.baeldung.algorithms.linkedlist;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+@RunWith(value = Parameterized.class)
+public class CycleRemovalWithoutCountingLoopNodesTest extends CycleDetectionTestBase {
+    boolean cycleExists;
+    Node<Integer> head;
+
+    public CycleRemovalWithoutCountingLoopNodesTest(Node<Integer> head, boolean cycleExists) {
+        super();
+        this.cycleExists = cycleExists;
+        this.head = head;
+    }
+
+    @Test
+    public void givenList_ifLoopExists_thenDetectAndRemoveLoop() {
+        Assert.assertEquals(cycleExists, CycleRemovalWithoutCountingLoopNodes.detectAndRemoveCycle(head));
+        Assert.assertFalse(CycleDetectionByFastAndSlowIterators.detectCycle(head).cycleExists);
+    }
+}
@@ -0,0 +1,2 @@
+### Relevant articles
+- [Introduction to Apache Shiro](http://www.baeldung.com/apache-shiro)
@@ -0,0 +1,2 @@
+### Relevant Articles:
+- [Introduction to Bootique](http://www.baeldung.com/bootique)
@@ -0,0 +1,35 @@
+package com.baeldung.stream;
+
+import static org.junit.Assert.fail;
+
+import java.util.Optional;
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+
+import org.junit.Test;
+
+public class SupplierStreamTest {
+
+    @Test(expected = IllegalStateException.class)
+    public void givenStream_whenStreamUsedTwice_thenThrowException() {
+        Stream<String> stringStream = Stream.of("A", "B", "C", "D");
+        Optional<String> result1 = stringStream.findAny();
+        System.out.println(result1.get());
+        Optional<String> result2 = stringStream.findFirst();
+        System.out.println(result2.get());
+    }
+
+    @Test
+    public void givenStream_whenUsingSupplier_thenNoExceptionIsThrown() {
+        try {
+            Supplier<Stream<String>> streamSupplier = () -> Stream.of("A", "B", "C", "D");
+            Optional<String> result1 = streamSupplier.get().findAny();
+            System.out.println(result1.get());
+            Optional<String> result2 = streamSupplier.get().findFirst();
+            System.out.println(result2.get());
+        } catch (IllegalStateException e) {
+            fail();
+        }
+    }
+
+}
@@ -8,7 +8,7 @@
 - [Java 9 Stream API Improvements](http://www.baeldung.com/java-9-stream-api)
 - [Java 9 Convenience Factory Methods for Collections](http://www.baeldung.com/java-9-collections-factory-methods) 
 - [New Stream Collectors in Java 9](http://www.baeldung.com/java9-stream-collectors)
- [Java 9 CompletableFuture API Improvements](http://www.baeldung.com/java9-completablefuture-api-improvements/)
+- [Java 9 CompletableFuture API Improvements](http://www.baeldung.com/java-9-completablefuture)
 - [Spring Security – Redirect to the Previous URL After Login](http://www.baeldung.com/spring-security-redirect-login)
 - [Java 9 Process API Improvements](http://www.baeldung.com/java-9-process-api)
 - [Introduction to Java 9 StackWalking API](http://www.baeldung.com/java-9-stackwalking-api)
@@ -16,3 +16,4 @@
 - [Java 9 Optional API Additions](http://www.baeldung.com/java-9-optional)
 - [Java 9 Reactive Streams](http://www.baeldung.com/java-9-reactive-streams)
 - [How to Get All Dates Between Two Dates?](http://www.baeldung.com/java-between-dates)
+- [Java 9 java.util.Objects Additions](http://www.baeldung.com/java-9-objects-new)
@@ -0,0 +1,24 @@
+package com.baeldung.java9.compactstring;
+
+import java.util.List;
+import static java.util.stream.Collectors.toList;
+import java.util.stream.IntStream;
+
+public class CompactStringDemo {
+
+    public static void main(String[] args) {
+        long startTime = System.currentTimeMillis();
+        List strings = IntStream.rangeClosed(1, 10_000_000)
+          .mapToObj(Integer::toString).collect(toList());
+        long totalTime = System.currentTimeMillis() - startTime;
+        System.out.println("Generated " + strings.size() + " strings in " 
+          + totalTime + " ms.");
+
+        startTime = System.currentTimeMillis();
+        String appended = (String) strings.stream().limit(100_000)
+          .reduce("", (left, right) -> left.toString() + right.toString());
+        totalTime = System.currentTimeMillis() - startTime;
+        System.out.println("Created string of length " + appended.length() 
+          + " in " + totalTime + " ms.");
+    }
+}
@@ -0,0 +1,30 @@
+package com.baeldung.concurrent.callable;
+
+
+import java.util.concurrent.Callable;
+
+public class FactorialTask implements Callable<Integer> {
+    int number;
+
+    public FactorialTask(int number) {
+        this.number = number;
+    }
+
+    public Integer call() throws InvalidParamaterException {
+        int fact=1;
+        if(number < 0)
+            throw new InvalidParamaterException("Number must be positive");
+
+        for(int count=number;count>1;count--){
+            fact=fact * count;
+        }
+
+        return fact;
+    }
+
+    private class InvalidParamaterException extends Exception {
+        public InvalidParamaterException(String message) {
+            super(message);
+        }
+    }
+}
@@ -0,0 +1,17 @@
+package com.baeldung.concurrent.runnable;
+
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class EventLoggingTask implements  Runnable{
+    private Logger logger = LoggerFactory.getLogger(EventLoggingTask.class);
+
+    @Override
+    public void run() {
+
+        String messge="Message read from the event queue";
+        logger.info("Message read from event queue is "+messge);
+
+    }
+}
@@ -0,0 +1,25 @@
+package com.baeldung.concurrent.runnable;
+
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+public class TaskRunner {
+
+    private static ExecutorService executorService;
+
+    public static void main(String[] args) {
+        executeTask();
+    }
+
+    private static void executeTask() {
+        executorService= Executors.newSingleThreadExecutor();
+
+        EventLoggingTask task = new EventLoggingTask();
+
+        Future future = executorService.submit(task);
+
+        executorService.shutdown();
+    }
+}
--- a/Show More
+++ b/Show More