Merge branch 'master' of https://github.com/eugenp/tutorials

README.md

@@ -32,7 +32,7 @@ Running a Spring Boot module
 ====================
 To run a Spring Boot module run the command: `mvn spring-boot:run` in the module directory
 
-#Running Tests
+###Running Tests
 
 The command `mvn clean install` will run the unit tests in a module.
 To run the integration tests, use the command `mvn clean install -Pintegration-lite-first`

algorithms-miscellaneous-3/README.md

@@ -6,4 +6,4 @@
 - [Practical Java Examples of the Big O Notation](http://www.baeldung.com/java-algorithm-complexity)
 - [Checking If a List Is Sorted in Java](https://www.baeldung.com/java-check-if-list-sorted)
 - [Checking if a Java Graph has a Cycle](https://www.baeldung.com/java-graph-has-a-cycle)
-- [A Guide to the Folding Technique](https://www.baeldung.com/folding-hashing-technique)
+- [A Guide to the Folding Technique in Java](https://www.baeldung.com/folding-hashing-technique)

algorithms-sorting/src/main/java/com/baeldung/algorithms/shellsort/ShellSort.java

@@ -0,0 +1,20 @@
+package com.baeldung.algorithms.shellsort;
+
+public class ShellSort {
+
+    public static void sort(int arrayToSort[]) {
+        int n = arrayToSort.length;
+
+        for (int gap = n / 2; gap > 0; gap /= 2) {
+            for (int i = gap; i < n; i++) {
+                int key = arrayToSort[i];
+                int j = i;
+                while (j >= gap && arrayToSort[j - gap] > key) {
+                    arrayToSort[j] = arrayToSort[j - gap];
+                    j -= gap;
+                }
+                arrayToSort[j] = key;
+            }
+        }
+    }
+}

algorithms-sorting/src/test/java/com/baeldung/algorithms/shellsort/ShellSortUnitTest.java

@@ -0,0 +1,17 @@
+package com.baeldung.algorithms.shellsort;
+
+import static org.junit.Assert.*;
+import static org.junit.Assert.assertArrayEquals;
+
+import org.junit.Test;
+
+public class ShellSortUnitTest {
+
+    @Test
+    public void givenUnsortedArray_whenShellSort_thenSortedAsc() {
+        int[] input = {41, 15, 82, 5, 65, 19, 32, 43, 8};
+        ShellSort.sort(input);
+        int[] expected = {5, 8, 15, 19, 32, 41, 43, 65, 82};
+        assertArrayEquals("the two arrays are not equal", expected, input);
+    }
+}

axon/pom.xml

@@ -18,12 +18,6 @@
             <groupId>org.axonframework</groupId>
             <artifactId>axon-spring-boot-starter</artifactId>
             <version>${axon.version}</version>
-            <exclusions>
-                <exclusion>
-                    <groupId>org.axonframework</groupId>
-                    <artifactId>axon-server-connector</artifactId>
-                </exclusion>
-            </exclusions>
         </dependency>
 
         <dependency>
@@ -58,7 +52,7 @@
     </dependencies>
 
     <properties>
-        <axon.version>4.0.3</axon.version>
+        <axon.version>4.1.2</axon.version>
     </properties>
 
 </project>

axon/src/main/java/com/baeldung/axon/commandmodel/OrderAggregate.java

@@ -13,6 +13,7 @@ import com.baeldung.axon.coreapi.commands.ShipOrderCommand;
 import com.baeldung.axon.coreapi.events.OrderConfirmedEvent;
 import com.baeldung.axon.coreapi.events.OrderPlacedEvent;
 import com.baeldung.axon.coreapi.events.OrderShippedEvent;
+import com.baeldung.axon.coreapi.exceptions.UnconfirmedOrderException;
 
 @Aggregate
 public class OrderAggregate {
@@ -34,7 +35,7 @@ public class OrderAggregate {
     @CommandHandler
     public void handle(ShipOrderCommand command) {
         if (!orderConfirmed) {
-            throw new IllegalStateException("Cannot ship an order which has not been confirmed yet.");
+            throw new UnconfirmedOrderException();
         }
 
         apply(new OrderShippedEvent(orderId));
@@ -43,12 +44,12 @@ public class OrderAggregate {
     @EventSourcingHandler
     public void on(OrderPlacedEvent event) {
         this.orderId = event.getOrderId();
-        orderConfirmed = false;
+        this.orderConfirmed = false;
     }
 
     @EventSourcingHandler
     public void on(OrderConfirmedEvent event) {
-        orderConfirmed = true;
+        this.orderConfirmed = true;
     }
 
     protected OrderAggregate() {

axon/src/main/java/com/baeldung/axon/coreapi/exceptions/UnconfirmedOrderException.java

@@ -0,0 +1,8 @@
+package com.baeldung.axon.coreapi.exceptions;
+
+public class UnconfirmedOrderException extends IllegalStateException {
+
+    public UnconfirmedOrderException() {
+        super("Cannot ship an order which has not been confirmed yet.");
+    }
+}

axon/src/main/java/com/baeldung/axon/querymodel/OrderedProductsEventHandler.java

@@ -5,6 +5,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import org.axonframework.config.ProcessingGroup;
 import org.axonframework.eventhandling.EventHandler;
 import org.axonframework.queryhandling.QueryHandler;
 import org.springframework.stereotype.Service;
@@ -16,6 +17,7 @@ import com.baeldung.axon.coreapi.queries.FindAllOrderedProductsQuery;
 import com.baeldung.axon.coreapi.queries.OrderedProduct;
 
 @Service
+@ProcessingGroup("ordered-products")
 public class OrderedProductsEventHandler {
 
     private final Map<String, OrderedProduct> orderedProducts = new HashMap<>();

axon/src/main/resources/application.properties

@@ -0,0 +1 @@
+spring.application.name=Order Management Service

axon/src/test/java/com/baeldung/axon/commandmodel/OrderAggregateUnitTest.java

@@ -2,6 +2,7 @@ package com.baeldung.axon.commandmodel;
 
 import java.util.UUID;
 
+import com.baeldung.axon.coreapi.exceptions.UnconfirmedOrderException;
 import org.axonframework.test.aggregate.AggregateTestFixture;
 import org.axonframework.test.aggregate.FixtureConfiguration;
 import org.junit.*;
@@ -41,12 +42,12 @@ public class OrderAggregateUnitTest {
     }
 
     @Test
-    public void givenOrderPlacedEvent_whenShipOrderCommand_thenShouldThrowIllegalStateException() {
+    public void givenOrderPlacedEvent_whenShipOrderCommand_thenShouldThrowUnconfirmedOrderException() {
         String orderId = UUID.randomUUID().toString();
         String product = "Deluxe Chair";
         fixture.given(new OrderPlacedEvent(orderId, product))
                .when(new ShipOrderCommand(orderId))
-               .expectException(IllegalStateException.class);
+               .expectException(UnconfirmedOrderException.class);
     }
 
     @Test

core-java-arrays/src/main/java/com/baeldung/array/looping/LoopDiagonally.java

@@ -0,0 +1,45 @@
+package com.baeldung.array.looping;
+
+public class LoopDiagonally {
+
+
+    public String loopDiagonally(String[][] twoDArray) {
+
+        int length = twoDArray.length;
+        int diagonalLines = (length + length) - 1;
+        int itemsInDiagonal = 0;
+        int midPoint = (diagonalLines / 2) + 1;
+        StringBuilder output = new StringBuilder();
+
+        for (int i = 1; i <= diagonalLines; i++) {
+
+            StringBuilder items = new StringBuilder();
+            int rowIndex;
+            int columnIndex;
+
+            if (i <= midPoint) {
+                itemsInDiagonal++;
+                for (int j = 0; j < itemsInDiagonal; j++) {
+                    rowIndex = (i - j) - 1;
+                    columnIndex = j;
+                    items.append(twoDArray[rowIndex][columnIndex]);
+                }
+            } else {
+                itemsInDiagonal--;
+                for (int j = 0; j < itemsInDiagonal; j++) {
+                    rowIndex = (length - 1) - j;
+                    columnIndex = (i - length) + j;
+                    items.append(twoDArray[rowIndex][columnIndex]);
+                }
+            }
+
+            if (i != diagonalLines) {
+                output.append(items).append(" ");
+            } else {
+                output.append(items);
+            }
+        }
+
+        return output.toString();
+    }
+}

core-java-arrays/src/test/java/com/baeldung/array/looping/LoopDiagonallyTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.array.looping;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class LoopDiagonallyTest {
+
+    @Test
+    public void twoArrayIsLoopedDiagonallyAsExpected() {
+
+        LoopDiagonally loopDiagonally = new LoopDiagonally();
+        String[][] twoDArray = {{"a", "b", "c"},
+                                {"d", "e", "f"},
+                                {"g", "h", "i"}};
+
+        String output = loopDiagonally.loopDiagonally(twoDArray);
+        assertEquals("a db gec hf i", output);
+    }
+}

core-java-modules/core-java-11/src/main/java/com/baeldung/predicate/not/README.md

@@ -0,0 +1,3 @@
+## Relevant articles:
+
+- [Negate a Predicate Method Reference with Java 11](https://www.baeldung.com/java-negate-predicate-method-reference)

core-java-modules/core-java-12/README.md

@@ -0,0 +1,3 @@
+## Relevant articles:
+
+- [String API Updates in Java 12](https://www.baeldung.com/java12-string-api)

core-java-modules/core-java-8/src/main/java/com/baeldung/java_8_features/groupingby/Tuple.java

@@ -0,0 +1,34 @@
+package com.baeldung.java_8_features.groupingby;
+
+public class Tuple {
+
+    private BlogPostType type;
+    private String author;
+    
+    public Tuple(BlogPostType type, String author) {
+        super();
+        this.type = type;
+        this.author = author;
+    }
+
+    public BlogPostType getType() {
+        return type;
+    }
+
+    public void setType(BlogPostType type) {
+        this.type = type;
+    }
+
+    public String getAuthor() {
+        return author;
+    }
+
+    public void setAuthor(String author) {
+        this.author = author;
+    }
+
+    @Override
+    public String toString() {
+        return "Tuple [type=" + type + ", author=" + author + ", getType()=" + getType() + ", getAuthor()=" + getAuthor() + ", getClass()=" + getClass() + ", hashCode()=" + hashCode() + ", toString()=" + super.toString() + "]";
+    }
+}

core-java-modules/core-java-8/src/test/java/com/baeldung/java8/optional/OptionalUnitTest.java

@@ -259,4 +259,15 @@ public class OptionalUnitTest {
         LOG.debug("Getting default value...");
         return "Default Value";
     }
+    
+//    Uncomment code when code base is compatiable with Java 11     
+//    @Test
+//    public void givenAnEmptyOptional_thenIsEmptyBehavesAsExpected() {
+//        Optional<String> opt = Optional.of("Baeldung");
+//        assertFalse(opt.isEmpty());
+//     
+//        opt = Optional.ofNullable(null);
+//        assertTrue(opt.isEmpty());
+//    }
+
 }

core-java-modules/core-java-collections-array-list/src/test/java/org/baeldung/java/collections/CoreJavaCollectionsUnitTest.java

@@ -42,7 +42,7 @@ public class CoreJavaCollectionsUnitTest {
     @Test(expected = UnsupportedOperationException.class)
     public final void givenUsingGuavaBuilder_whenUnmodifiableListIsCreatedFromOriginal_thenNoLongerModifiable() {
         final List<String> list = new ArrayList<String>(Arrays.asList("one", "two", "three"));
-        final ImmutableList<Object> unmodifiableList = ImmutableList.builder().addAll(list).build();
+        final ImmutableList<String> unmodifiableList = ImmutableList.<String>builder().addAll(list).build();
         unmodifiableList.add("four");
     }
 

core-java-modules/core-java-concurrency-basic/README.md

@@ -17,3 +17,4 @@
 - [Runnable vs. Callable in Java](http://www.baeldung.com/java-runnable-callable)
 - [What is Thread-Safety and How to Achieve it?](https://www.baeldung.com/java-thread-safety)
 - [How to Start a Thread in Java](https://www.baeldung.com/java-start-thread)
+- [How to Delay Code Execution in Java](https://www.baeldung.com/java-delay-code-execution)

core-java-modules/core-java-exceptions/README.md

@@ -0,0 +1,3 @@
+## Relevant articles:
+
+- [Will an Error Be Caught by Catch Block in Java?](https://www.baeldung.com/java-error-catch)

core-java-modules/core-java-lambdas/README.md

@@ -0,0 +1,3 @@
+## Relevant articles:
+
+- [Why Do Local Variables Used in Lambdas Have to Be Final or Effectively Final?](https://www.baeldung.com/java-lambda-effectively-final-local-variables)

core-java-modules/core-java-lang-oop/src/main/java/com/baeldung/constructors/BankAccount.java

@@ -54,3 +54,15 @@ class BankAccountCopyConstructor extends BankAccount {
         this.balance = 0.0f;
     }
 }
+
+class BankAccountChainedConstructors extends BankAccount {
+    public BankAccountChainedConstructors(String name, LocalDateTime opened, double balance) {
+        this.name = name;
+        this.opened = opened;
+        this.balance = balance;
+    }
+
+    public BankAccountChainedConstructors(String name) {
+        this(name, LocalDateTime.now(), 0.0f);
+    }
+}

core-java-modules/core-java-lang-oop/src/test/java/com/baeldung/constructors/ConstructorUnitTest.java

@@ -1,15 +1,14 @@
 package com.baeldung.constructors;
 
-import com.baeldung.constructors.*;
+import com.google.common.collect.Comparators;
+import org.junit.Test;
 
-import java.util.logging.Logger;
 import java.time.LocalDateTime;
 import java.time.Month;
+import java.util.ArrayList;
+import java.util.logging.Logger;
 
-import org.junit.Test;
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatCode;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.assertj.core.api.Assertions.*;
 
 public class ConstructorUnitTest {
     final static Logger LOGGER = Logger.getLogger(ConstructorUnitTest.class.getName());
@@ -17,26 +16,28 @@ public class ConstructorUnitTest {
     @Test
     public void givenNoExplicitContructor_whenUsed_thenFails() {
         BankAccount account = new BankAccount();
-        assertThatThrownBy(() -> { account.toString(); }).isInstanceOf(Exception.class);
+        assertThatThrownBy(() -> {
+            account.toString();
+        }).isInstanceOf(Exception.class);
     }
 
     @Test
     public void givenNoArgumentConstructor_whenUsed_thenSucceeds() {
         BankAccountEmptyConstructor account = new BankAccountEmptyConstructor();
         assertThatCode(() -> {
-                account.toString();
-            }).doesNotThrowAnyException();
+            account.toString();
+        }).doesNotThrowAnyException();
     }
 
     @Test
     public void givenParameterisedConstructor_whenUsed_thenSucceeds() {
         LocalDateTime opened = LocalDateTime.of(2018, Month.JUNE, 29, 06, 30, 00);
         BankAccountParameterizedConstructor account =
-            new BankAccountParameterizedConstructor("Tom", opened, 1000.0f);
-        
+                new BankAccountParameterizedConstructor("Tom", opened, 1000.0f);
+
         assertThatCode(() -> {
-                account.toString();
-            }).doesNotThrowAnyException();
+            account.toString();
+        }).doesNotThrowAnyException();
     }
 
     @Test
@@ -47,7 +48,16 @@ public class ConstructorUnitTest {
 
         assertThat(account.getName()).isEqualTo(newAccount.getName());
         assertThat(account.getOpened()).isNotEqualTo(newAccount.getOpened());
-        
+
         assertThat(newAccount.getBalance()).isEqualTo(0.0f);
     }
+
+    @Test
+    public void givenChainedConstructor_whenUsed_thenMaintainsLogic() {
+        BankAccountChainedConstructors account = new BankAccountChainedConstructors("Tim");
+        BankAccountChainedConstructors newAccount = new BankAccountChainedConstructors("Tim", LocalDateTime.now(), 0.0f);
+
+        assertThat(account.getName()).isEqualTo(newAccount.getName());
+        assertThat(account.getBalance()).isEqualTo(newAccount.getBalance());
+    }
 }

core-java-modules/core-java-lang/README.md

@@ -18,7 +18,6 @@
 - [A Guide to Inner Interfaces in Java](http://www.baeldung.com/java-inner-interfaces)
 - [Recursion In Java](http://www.baeldung.com/java-recursion)
 - [A Guide to the finalize Method in Java](http://www.baeldung.com/java-finalize)
-- [A Guide to Java Enums](http://www.baeldung.com/a-guide-to-java-enums)
 - [Infinite Loops in Java](http://www.baeldung.com/infinite-loops-java)
 - [Quick Guide to java.lang.System](http://www.baeldung.com/java-lang-system)
 - [Using Java Assertions](http://www.baeldung.com/java-assert)

core-java-modules/core-java-os/src/main/java/com/baeldung/core/pwd/CurrentDirectoryFetcher.java

@@ -0,0 +1,40 @@
+package com.baeldung.core.pwd;
+
+import java.io.File;
+import java.nio.file.FileSystems;
+import java.nio.file.Paths;
+
+public final class CurrentDirectoryFetcher {
+
+    public static void main(String[] args) {
+        System.out.printf("Current Directory Using Java System API: %s%n", currentDirectoryUsingSystemProperties());
+
+        System.out.printf("Current Directory Using Java IO File API: %s%n", currentDirectoryUsingFile());
+
+        System.out.printf("Current Directory Using Java NIO FileSystems API: %s%n", currentDirectoryUsingFileSystems());
+
+        System.out.printf("Current Directory Using Java NIO Paths API: %s%n", currentDirectoryUsingPaths());
+    }
+
+    public static String currentDirectoryUsingSystemProperties() {
+        return System.getProperty("user.dir");
+    }
+
+    public static String currentDirectoryUsingPaths() {
+        return Paths.get("")
+            .toAbsolutePath()
+            .toString();
+    }
+
+    public static String currentDirectoryUsingFileSystems() {
+        return FileSystems.getDefault()
+            .getPath("")
+            .toAbsolutePath()
+            .toString();
+    }
+
+    public static String currentDirectoryUsingFile() {
+        return new File("").getAbsolutePath();
+    }
+
+}

core-java-modules/core-java-os/src/test/java/com/baeldung/core/pwd/CurrentDirectoryFetcherTest.java

@@ -0,0 +1,34 @@
+package com.baeldung.core.pwd;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class CurrentDirectoryFetcherTest {
+
+    private static final String CURRENT_DIR = "core-java-os";
+
+    @Test
+    public void whenUsingSystemProperties_thenReturnCurrentDirectory() {
+        assertTrue(CurrentDirectoryFetcher.currentDirectoryUsingSystemProperties()
+            .endsWith(CURRENT_DIR));
+    }
+
+    @Test
+    public void whenUsingJavaNioPaths_thenReturnCurrentDirectory() {
+        assertTrue(CurrentDirectoryFetcher.currentDirectoryUsingPaths()
+            .endsWith(CURRENT_DIR));
+    }
+
+    @Test
+    public void whenUsingJavaNioFileSystems_thenReturnCurrentDirectory() {
+        assertTrue(CurrentDirectoryFetcher.currentDirectoryUsingFileSystems()
+            .endsWith(CURRENT_DIR));
+    }
+
+    @Test
+    public void whenUsingJavaIoFile_thenReturnCurrentDirectory() {
+        assertTrue(CurrentDirectoryFetcher.currentDirectoryUsingFile()
+            .endsWith(CURRENT_DIR));
+    }
+}

core-java-modules/core-java/README.md

@@ -37,7 +37,6 @@
 - [Common Java Exceptions](http://www.baeldung.com/java-common-exceptions)
 - [Throw Exception in Optional in Java 8](https://www.baeldung.com/java-optional-throw-exception)
 - [Merging java.util.Properties Objects](https://www.baeldung.com/java-merging-properties)
-- [Merging java.util.Properties Objects](https://www.baeldung.com/java-merging-properties)
 - [Java – Try with Resources](https://www.baeldung.com/java-try-with-resources)
 - [Abstract Classes in Java](https://www.baeldung.com/java-abstract-class)
 - [Guide to Character Encoding](https://www.baeldung.com/java-char-encoding)

custom-pmd/src/main/java/org/baeldung/pmd/UnitTestNamingConventionRule.java

@@ -22,6 +22,10 @@ public class UnitTestNamingConventionRule extends AbstractJavaRule {
         String className = node.getImage();
         Objects.requireNonNull(className);
 
+        if (className.endsWith("SpringContextTest")) {
+            return data;
+        }
+        
         if (className.endsWith("Tests")
                 || (className.endsWith("Test") && allowedEndings.stream().noneMatch(className::endsWith))) {
             addViolation(data, node);

jackson-simple/src/test/java/com/baeldung/jackson/test/JacksonSerializationIgnoreUnitTest.java

@@ -165,7 +165,7 @@ public class JacksonSerializationIgnoreUnitTest {
     }
 
     @Test
-    public final void givenIgnoringNullFieldsOnClass_whenWritingObjectWithNullField_thenFieldIsIgnored() throws JsonProcessingException {
+    public final void givenNullsIgnoredOnClass_whenWritingObjectWithNullField_thenIgnored() throws JsonProcessingException {
         final ObjectMapper mapper = new ObjectMapper();
         final MyDtoIgnoreNull dtoObject = new MyDtoIgnoreNull();
 
@@ -178,7 +178,7 @@ public class JacksonSerializationIgnoreUnitTest {
     }
 
     @Test
-    public final void givenIgnoringNullFieldsGlobally_whenWritingObjectWithNullField_thenIgnored() throws JsonProcessingException {
+    public final void givenNullsIgnoredGlobally_whenWritingObjectWithNullField_thenIgnored() throws JsonProcessingException {
         final ObjectMapper mapper = new ObjectMapper();
         mapper.setSerializationInclusion(Include.NON_NULL);
         final MyDto dtoObject = new MyDto();

java-strings-2/README.MD

@@ -4,3 +4,4 @@
 - [Check If a String Contains a Substring](https://www.baeldung.com/java-string-contains-substring)
 - [Removing Stopwords from a String in Java](https://www.baeldung.com/java-string-remove-stopwords)
 - [Blank and Empty Strings in Java](https://www.baeldung.com/java-blank-empty-strings)
+- [String Initialization in Java](https://www.baeldung.com/java-string-initialization)