Merge branch 'master' into master

2017-09-09 21:03:46 +02:00
parent 1d90d18271 f01d1e257e
commit 33dfe041ff
861 changed files with 22523 additions and 2700 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/)**
@@ -0,0 +1,55 @@
+package com.baeldung.algorithms.binarysearch;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+public class BinarySearch {
+
+    public int runBinarySearchIteratively(int[] sortedArray, int key, int low, int high) {
+
+        int index = Integer.MAX_VALUE;
+
+        while (low <= high) {
+
+            int mid = (low + high) / 2;
+
+            if (sortedArray[mid] < key) {
+                low = mid + 1;
+            } else if (sortedArray[mid] > key) {
+                high = mid - 1;
+            } else if (sortedArray[mid] == key) {
+                index = mid;
+                break;
+            }
+        }
+        return index;
+    }
+
+    public int runBinarySearchRecursively(int[] sortedArray, int key, int low, int high) {
+
+        int middle = (low + high) / 2;
+        if (high < low) {
+            return -1;
+        }
+
+        if (key == sortedArray[middle]) {
+          return middle;
+        } else if (key < sortedArray[middle]) {
+          return runBinarySearchRecursively(sortedArray, key, low, middle - 1);
+        } else {
+          return runBinarySearchRecursively(sortedArray, key, middle + 1, high);
+        }
+    }
+
+    public int runBinarySearchUsingJavaArrays(int[] sortedArray, Integer key) {
+        int index = Arrays.binarySearch(sortedArray, key);
+        return index;
+    }
+
+    public int runBinarySearchUsingJavaCollections(List<Integer> sortedList, Integer key) {
+        int index = Collections.binarySearch(sortedList, key);
+        return index;
+    }
+
+}
@@ -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()));
+	}
+
+}
@@ -0,0 +1,43 @@
+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 {
+
+    int[] sortedArray = { 0, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 9 };
+    int key = 6;
+    int expectedIndexForSearchKey = 7;
+    int low = 0;
+    int high = sortedArray.length - 1;
+    List<Integer> sortedList = Arrays.asList(0, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 9);
+    
+    @Test
+    public void givenASortedArrayOfIntegers_whenBinarySearchRunIterativelyForANumber_thenGetIndexOfTheNumber() {
+        BinarySearch binSearch = new BinarySearch();
+        Assert.assertEquals(expectedIndexForSearchKey, binSearch.runBinarySearchIteratively(sortedArray, key, low, high));
+    }
+
+    @Test
+    public void givenASortedArrayOfIntegers_whenBinarySearchRunRecursivelyForANumber_thenGetIndexOfTheNumber() {
+        BinarySearch binSearch = new BinarySearch();
+        Assert.assertEquals(expectedIndexForSearchKey, binSearch.runBinarySearchRecursively(sortedArray, key, low, high));
+    }
+    
+    @Test
+    public void givenASortedArrayOfIntegers_whenBinarySearchRunUsingArraysClassStaticMethodForANumber_thenGetIndexOfTheNumber() {
+        BinarySearch binSearch = new BinarySearch();
+        Assert.assertEquals(expectedIndexForSearchKey, binSearch.runBinarySearchUsingJavaArrays(sortedArray, key));
+    }
+    
+    @Test
+    public void givenASortedListOfIntegers_whenBinarySearchRunUsingCollectionsClassStaticMethodForANumber_thenGetIndexOfTheNumber() {
+        BinarySearch binSearch = new BinarySearch();
+        Assert.assertEquals(expectedIndexForSearchKey, binSearch.runBinarySearchUsingJavaCollections(sortedList, key));
+    }
+    
+}
@@ -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 +1,4 @@
+
+/.idea/
+/target/
+/apache-shiro.iml
@@ -0,0 +1,78 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.baeldung</groupId>
+    <artifactId>apache-shiro</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>1.5.2.RELEASE</version>
+    </parent>
+
+    <properties>
+        <apache-shiro-core-version>1.4.0</apache-shiro-core-version>
+        <log4j-version>1.2.17</log4j-version>
+        <slf4j-version>1.7.25</slf4j-version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-freemarker</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.shiro</groupId>
+            <artifactId>shiro-spring-boot-web-starter</artifactId>
+            <version>${apache-shiro-core-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.shiro</groupId>
+            <artifactId>shiro-core</artifactId>
+            <version>${apache-shiro-core-version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>jcl-over-slf4j</artifactId>
+            <version>${slf4j-version}</version>
+            <scope>runtime</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-log4j12</artifactId>
+            <version>${slf4j-version}</version>
+            <scope>runtime</scope>
+        </dependency>
+        <dependency>
+            <groupId>log4j</groupId>
+            <artifactId>log4j</artifactId>
+            <version>${log4j-version}</version>
+            <scope>runtime</scope>
+        </dependency>
+
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.6.2</version>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    
+</project>
@@ -0,0 +1,85 @@
+package com.baeldung;
+
+import org.apache.shiro.SecurityUtils;
+import org.apache.shiro.authc.*;
+import org.apache.shiro.mgt.DefaultSecurityManager;
+import org.apache.shiro.mgt.SecurityManager;
+import org.apache.shiro.realm.Realm;
+import org.apache.shiro.realm.text.IniRealm;
+import org.apache.shiro.session.Session;
+import org.apache.shiro.subject.Subject;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Main {
+
+    private static final transient Logger log = LoggerFactory.getLogger(Main.class);
+
+    public static void main(String[] args) {
+
+        Realm realm = new MyCustomRealm();
+        SecurityManager securityManager = new DefaultSecurityManager(realm);
+
+        SecurityUtils.setSecurityManager(securityManager);
+        Subject currentUser = SecurityUtils.getSubject();
+
+        if (!currentUser.isAuthenticated()) {
+          UsernamePasswordToken token 
+            = new UsernamePasswordToken("user", "password");
+          token.setRememberMe(true);
+          try {
+              currentUser.login(token);
+          } catch (UnknownAccountException uae) {
+              log.error("Username Not Found!", uae);
+          } catch (IncorrectCredentialsException ice) {
+              log.error("Invalid Credentials!", ice);
+          } catch (LockedAccountException lae) {
+              log.error("Your Account is Locked!", lae);
+          } catch (AuthenticationException ae) {
+              log.error("Unexpected Error!", ae);
+          }
+        }
+
+        log.info("User [" + currentUser.getPrincipal() + "] logged in successfully.");
+
+        if (currentUser.hasRole("admin")) {
+            log.info("Welcome Admin");
+        } else if(currentUser.hasRole("editor")) {
+            log.info("Welcome, Editor!");
+        } else if(currentUser.hasRole("author")) {
+            log.info("Welcome, Author");
+        } else {
+            log.info("Welcome, Guest");
+        }
+
+        if(currentUser.isPermitted("articles:compose")) {
+            log.info("You can compose an article");
+        } else {
+            log.info("You are not permitted to compose an article!");
+        }
+
+        if(currentUser.isPermitted("articles:save")) {
+            log.info("You can save articles");
+        } else {
+            log.info("You can not save articles");
+        }
+
+        if(currentUser.isPermitted("articles:publish")) {
+            log.info("You can publish articles");
+        } else {
+            log.info("You can not publish articles");
+        }
+
+        Session session = currentUser.getSession();
+        session.setAttribute("key", "value");
+        String value = (String) session.getAttribute("key");
+        if (value.equals("value")) {
+            log.info("Retrieved the correct value! [" + value + "]");
+        }
+
+        currentUser.logout();
+
+        System.exit(0);
+    }
+
+}
@@ -0,0 +1,102 @@
+package com.baeldung;
+
+import org.apache.shiro.authc.*;
+import org.apache.shiro.authz.AuthorizationInfo;
+import org.apache.shiro.authz.SimpleAuthorizationInfo;
+import org.apache.shiro.realm.jdbc.JdbcRealm;
+import org.apache.shiro.subject.PrincipalCollection;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.util.*;
+
+public class MyCustomRealm extends JdbcRealm {
+
+    private Map<String, String> credentials = new HashMap<>();
+    private Map<String, Set<String>> roles = new HashMap<>();
+    private Map<String, Set<String>> perm = new HashMap<>();
+
+    {
+      credentials.put("user", "password");
+      credentials.put("user2", "password2");
+      credentials.put("user3", "password3");
+
+      roles.put("user", new HashSet<>(Arrays.asList("admin")));
+      roles.put("user2", new HashSet<>(Arrays.asList("editor")));
+      roles.put("user3", new HashSet<>(Arrays.asList("author")));
+
+      perm.put("admin", new HashSet<>(Arrays.asList("*")));
+      perm.put("editor", new HashSet<>(Arrays.asList("articles:*")));
+      perm.put("author",
+        new HashSet<>(Arrays.asList("articles:compose",
+          "articles:save")));
+
+    }
+
+    @Override
+    protected AuthenticationInfo doGetAuthenticationInfo(AuthenticationToken token)
+      throws AuthenticationException {
+
+        UsernamePasswordToken uToken = (UsernamePasswordToken) token;
+
+        if(uToken.getUsername() == null
+          || uToken.getUsername().isEmpty()
+          || !credentials.containsKey(uToken.getUsername())
+          ) {
+            throw new UnknownAccountException("username not found!");
+        }
+
+
+        return new SimpleAuthenticationInfo(
+          uToken.getUsername(), credentials.get(uToken.getUsername()),
+          getName());
+    }
+
+    @Override
+    protected AuthorizationInfo doGetAuthorizationInfo(PrincipalCollection principals) {
+        Set<String> roleNames = new HashSet<>();
+        Set<String> permissions = new HashSet<>();
+
+        principals.forEach(p -> {
+            try {
+                Set<String> roles = getRoleNamesForUser(null, (String) p);
+                roleNames.addAll(roles);
+                permissions.addAll(getPermissions(null, null,roles));
+            } catch (SQLException e) {
+                e.printStackTrace();
+            }
+        });
+
+        SimpleAuthorizationInfo info = new SimpleAuthorizationInfo(roleNames);
+        info.setStringPermissions(permissions);
+        return info;
+    }
+
+    @Override
+    protected Set<String> getRoleNamesForUser(Connection conn, String username) throws SQLException {
+        if(!roles.containsKey(username)) {
+            throw new SQLException("username not found!");
+        }
+
+       return roles.get(username);
+    }
+
+    @Override
+    protected Set<String> getPermissions(Connection conn, String username, Collection<String> roleNames) throws SQLException {
+        for (String role : roleNames) {
+            if (!perm.containsKey(role)) {
+                throw new SQLException("role not found!");
+            }
+        }
+
+        Set<String> finalSet = new HashSet<>();
+        for (String role : roleNames) {
+            finalSet.addAll(perm.get(role));
+        }
+
+        return finalSet;
+    }
+
+}
@@ -0,0 +1,45 @@
+package com.baeldung;
+
+import org.apache.shiro.realm.Realm;
+import org.apache.shiro.spring.web.config.DefaultShiroFilterChainDefinition;
+import org.apache.shiro.spring.web.config.ShiroFilterChainDefinition;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.annotation.Bean;
+
+/**
+ * Created by smatt on 21/08/2017.
+ */
+@SpringBootApplication
+public class ShiroSpringApplication {
+
+    private static final transient Logger log = LoggerFactory.getLogger(ShiroSpringApplication.class);
+
+    public static void main(String... args) {
+        SpringApplication.run(ShiroSpringApplication.class, args);
+    }
+
+
+    @Bean
+    public Realm realm() {
+        return new MyCustomRealm();
+    }
+
+
+    @Bean
+    public ShiroFilterChainDefinition shiroFilterChainDefinition() {
+        DefaultShiroFilterChainDefinition filter
+          = new DefaultShiroFilterChainDefinition();
+
+        filter.addPathDefinition("/secure", "authc");
+        filter.addPathDefinition("/**", "anon");
+
+        return filter;
+    }
+
+
+
+
+}
@@ -0,0 +1,105 @@
+package com.baeldung.controllers;
+
+import com.baeldung.models.UserCredentials;
+import org.apache.shiro.SecurityUtils;
+import org.apache.shiro.authc.AuthenticationException;
+import org.apache.shiro.authc.UsernamePasswordToken;
+import org.apache.shiro.subject.Subject;
+import org.springframework.stereotype.Controller;
+import org.springframework.ui.ModelMap;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
+import org.springframework.web.servlet.mvc.support.RedirectAttributes;
+
+import javax.servlet.http.HttpServletRequest;
+
+@Controller
+public class ShiroSpringController {
+
+
+
+    @GetMapping("/")
+    public String index() {
+       return "index";
+    }
+
+
+    @RequestMapping( value = "/login", method = {RequestMethod.GET, RequestMethod.POST})
+    public String login(HttpServletRequest req, UserCredentials cred, RedirectAttributes attr) {
+
+      if(req.getMethod().equals(RequestMethod.GET.toString())) {
+        return "login";
+      }
+      else {
+
+        Subject subject = SecurityUtils.getSubject();
+
+        if(!subject.isAuthenticated()) {
+          UsernamePasswordToken token = new UsernamePasswordToken(
+            cred.getUsername(), cred.getPassword(), cred.isRememberMe());
+          try {
+            subject.login(token);
+          } catch (AuthenticationException ae) {
+              ae.printStackTrace();
+              attr.addFlashAttribute("error", "Invalid Credentials");
+              return "redirect:/login";
+          }
+        }
+
+        return "redirect:/secure";
+      }
+    }
+
+
+    @GetMapping("/secure")
+    public String secure(ModelMap modelMap) {
+
+        Subject currentUser = SecurityUtils.getSubject();
+        String role = "", permission = "";
+
+        if(currentUser.hasRole("admin")) {
+            role = role  + "You are an Admin";
+        }
+        else if(currentUser.hasRole("editor")) {
+            role = role + "You are an Editor";
+        }
+        else if(currentUser.hasRole("author")) {
+            role = role + "You are an Author";
+        }
+
+        if(currentUser.isPermitted("articles:compose")) {
+            permission = permission + "You can compose an article, ";
+        } else {
+            permission = permission + "You are not permitted to compose an article!, ";
+        }
+
+        if(currentUser.isPermitted("articles:save")) {
+            permission = permission + "You can save articles, ";
+        } else {
+            permission = permission + "\nYou can not save articles, ";
+        }
+
+        if(currentUser.isPermitted("articles:publish")) {
+            permission = permission  + "\nYou can publish articles";
+        } else {
+            permission = permission + "\nYou can not publish articles";
+        }
+
+        modelMap.addAttribute("username", currentUser.getPrincipal());
+        modelMap.addAttribute("permission", permission);
+        modelMap.addAttribute("role", role);
+
+        return "secure";
+    }
+
+
+    @PostMapping("/logout")
+    public String logout() {
+       Subject subject = SecurityUtils.getSubject();
+       subject.logout();
+       return "redirect:/";
+    }
+
+}
@@ -0,0 +1,40 @@
+package com.baeldung.models;
+
+public class UserCredentials {
+
+    private String username;
+    private String password;
+    private boolean rememberMe = false;
+
+    public UserCredentials() {}
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) {
+        this.username = username;
+    }
+
+    public String getPassword() {
+        return password;
+    }
+
+    public void setPassword(String password) {
+        this.password = password;
+    }
+
+    public boolean isRememberMe() {
+        return rememberMe;
+    }
+
+    public void setRememberMe(boolean rememberMe) {
+        this.rememberMe = rememberMe;
+    }
+
+    @Override
+    public String toString() {
+        return "username = " + getUsername()
+                + "\nrememberMe = " + isRememberMe();
+    }
+}
@@ -0,0 +1,11 @@
+server.port=9000
+server.servlet-path=/
+server.context-path=/
+
+#shiro-spring-boot-config
+shiro.loginUrl = /login
+shiro.successUrl = /secure
+shiro.unauthorizedUrl = /login
+
+#freemarker
+spring.freemarker.suffix=.ftl
--- a/Show More
+++ b/Show More