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DOHA
2018-04-25 21:21:47 +02:00
parent dd4000c3d1 e5aff9cf81
commit 238618abb5
123 changed files with 2594 additions and 1752 deletions
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algorithms/README.md
+1
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@@ -20,3 +20,4 @@
- [A Maze Solver in Java](http://www.baeldung.com/java-solve-maze)
- [Create a Sudoku Solver in Java](http://www.baeldung.com/java-sudoku)
- [Displaying Money Amounts in Words](http://www.baeldung.com/java-money-into-words)
- [A Collaborative Filtering Recommendation System in Java](http://www.baeldung.com/java-collaborative-filtering-recommendations)
algorithms/src/main/java/com/baeldung/algorithms/RunAlgorithm.java
+8
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@@ -6,6 +6,7 @@ import com.baeldung.algorithms.ga.annealing.SimulatedAnnealing;
import com.baeldung.algorithms.ga.ant_colony.AntColonyOptimization;
import com.baeldung.algorithms.ga.binary.SimpleGeneticAlgorithm;
import com.baeldung.algorithms.slope_one.SlopeOne;
import com.baeldung.algorithms.pairsaddupnumber.FindPairs;
public class RunAlgorithm {
@@ -17,6 +18,7 @@ public class RunAlgorithm {
System.out.println("3 - Simple Genetic Algorithm");
System.out.println("4 - Ant Colony");
System.out.println("5 - Dijkstra");
System.out.println("6 - All pairs in an array that add up to a given sum");
int decision = in.nextInt();
switch (decision) {
case 1:
@@ -37,6 +39,12 @@ public class RunAlgorithm {
case 5:
System.out.println("Please run the DijkstraAlgorithmTest.");
break;
case 6:
final FindPairs findPairs = new FindPairs();
final int[] input = {1, 4, 3, 2, 1, 4, 4, 3, 3};
final int sum = 6;
findPairs.execute(input, sum);
break;
default:
System.out.println("Unknown option");
break;
algorithms/src/main/java/com/baeldung/algorithms/pairsaddupnumber/DifferentPairs.java
+72
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@@ -0,0 +1,72 @@
package com.baeldung.algorithms.pairsaddupnumber;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.IntStream;
/**
* Find all different pairs of numbers in an array that add up to a given sum - Complexity O(n)
*/
public class DifferentPairs {
/**
* Show all different pairs using traditional "for" loop
*
* @param input - number's array
* @param sum - given sum
* @return - number's array with all existing pairs. This list will contain just one pair's element because
* the other one can be calculated with SUM - element_1 = element_2
*/
public static List<Integer> findPairsWithForLoop(int[] input, int sum) {
final List<Integer> allDifferentPairs = new ArrayList<>();
// Aux. hash map
final Map<Integer, Integer> pairs = new HashMap();
for (int i : input) {
if (pairs.containsKey(i)) {
if (pairs.get(i) != null) {
// Add pair to returned list
allDifferentPairs.add(i);
}
// Mark pair as added to prevent duplicates
pairs.put(sum - i, null);
} else if (!pairs.containsValue(i)) {
// Add pair to aux. hash map
pairs.put(sum - i, i);
}
}
return allDifferentPairs;
}
/**
* Show all different pairs using Java 8 stream API
*
* @param input - number's array
* @param sum - given sum
* @return - number's array with all existing pairs. This list will contain just one pair's element because
* the other one can be calculated with SUM - element_1 = element_2
*/
public static List<Integer> findPairsWithStreamApi(int[] input, int sum) {
final List<Integer> allDifferentPairs = new ArrayList<>();
// Aux. hash map
final Map<Integer, Integer> pairs = new HashMap();
IntStream.range(0, input.length).forEach(i -> {
if (pairs.containsKey(input[i])) {
if (pairs.get(input[i]) != null) {
// Add pair to returned list
allDifferentPairs.add(input[i]);
}
// Mark pair as added to prevent duplicates
pairs.put(sum - input[i], null);
} else if (!pairs.containsValue(input[i])) {
// Add pair to aux. hash map
pairs.put(sum - input[i], input[i]);
}
}
);
return allDifferentPairs;
}
}
algorithms/src/main/java/com/baeldung/algorithms/pairsaddupnumber/ExistingPairs.java
+51
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@@ -0,0 +1,51 @@
package com.baeldung.algorithms.pairsaddupnumber;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;
/**
* Find all existing pairs of numbers in an array that add up to a given sum - Complexity O(n^2) "Brute force"
*/
public class ExistingPairs {
/**
* Show all existing pairs using traditional "for" loop
*
* @param input - number's array
* @param sum - given sum
* @return - number's array with all existing pairs. This list will contain just one pair's element because
* the other one can be calculated with SUM - element_1 = element_2
*/
public static List<Integer> findPairsWithForLoop(int[] input, int sum) {
final List<Integer> allExistingPairs = new ArrayList<>();
for (int i = 0; i < input.length; i++) {
for (int j = 0; j < input.length; j++) {
if (j != i && (input[i] + input[j]) == sum) {
allExistingPairs.add(input[i]);
}
}
}
return allExistingPairs;
}
/**
* Show all existing pairs using Java 8 stream API
*
* @param input - number's array
* @param sum - given sum
* @return - number's array with all existing pairs. This list will contain just one pair's element because
* the other one can be calculated with SUM - element_1 = element_2
*/
public static List<Integer> findPairsWithStreamApi(int[] input, int sum) {
final List<Integer> allExistingPairs = new ArrayList<>();
IntStream.range(0, input.length).forEach(i ->
IntStream.range(0, input.length)
.filter(j -> i != j && input[i] + input[j] == sum)
.forEach(j -> allExistingPairs.add(input[i]))
);
return allExistingPairs;
}
}
algorithms/src/main/java/com/baeldung/algorithms/pairsaddupnumber/FindPairs.java
+74
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@@ -0,0 +1,74 @@
package com.baeldung.algorithms.pairsaddupnumber;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;
public class FindPairs {
public void execute(int[] input, int sum) {
final StringBuilder inputArray = new StringBuilder();
inputArray.append("{");
IntStream.range(0, input.length).forEach(i -> inputArray.append(input[i] + ", "));
inputArray.append("}");
System.out.println(" Given number array: " + inputArray.toString());
System.out.println(" Given sum: " + sum);
/* Call services */
getDifferentPairs(input, sum);
getExistingPairs(input, sum);
}
/**
* Print all existing pairs for the given inputs: input array & sum number
*/
private static void getExistingPairs(int[] input, int sum) {
List<Integer> pairs = new ArrayList<>();
System.out.println("~ All existing pairs ~");
/* Traditional FOR loop */
// Call method
pairs = ExistingPairs.findPairsWithForLoop(input, sum);
// Create a pretty printing
final StringBuilder output1 = new StringBuilder();
pairs.forEach((pair) -> output1.append("{" + pair + ", " + (sum - pair) + "}, "));
// Print result
System.out.println("Traditional \"for\" loop: " + output1.toString().substring(0, output1.length() - 2));
/* Java 8 stream API */
// Call the method
pairs = ExistingPairs.findPairsWithStreamApi(input, sum);
// Create a pretty printing
final StringBuilder output2 = new StringBuilder();
pairs.forEach((pair) -> output2.append("{" + pair + ", " + (sum - pair) + "}, "));
// Print result
System.out.println("Java 8 streams API: " + output2.toString().substring(0, output2.length() - 2));
}
/**
* Print all different pairs for the given inputs: input array & sum number
*/
private static void getDifferentPairs(int[] input, int sum) {
List<Integer> pairs = new ArrayList<>();
System.out.println("~ All different pairs ~");
/* Traditional FOR loop */
// Call method
pairs = DifferentPairs.findPairsWithForLoop(input, sum);
// Create a pretty printing
final StringBuilder output3 = new StringBuilder();
pairs.forEach((pair) -> output3.append("{" + pair + ", " + (sum - pair) + "}, "));
// Print result
System.out.println("Traditional \"for\" loop: " + output3.toString().substring(0, output3.length() - 2));
/* Java 8 stream API */
// Call method
pairs = DifferentPairs.findPairsWithStreamApi(input, sum);
// Create a pretty printing
final StringBuilder output4 = new StringBuilder();
pairs.forEach((pair) -> output4.append("{" + pair + ", " + (sum - pair) + "}, "));
// Print result
System.out.println("Java 8 streams API: " + output4.toString().substring(0, output4.length() - 2));
}
}
algorithms/src/test/java/com/baeldung/algorithms/pairsaddupnumber/DifferentPairsUnitTest.java
+39
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@@ -0,0 +1,39 @@
package com.baeldung.algorithms.pairsaddupnumber;
import org.junit.Test;
import java.util.List;
import static org.assertj.core.api.Assertions.assertThat;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
public class DifferentPairsUnitTest {
/* All different pairs */
@Test
public void whenTraditionalLoop_thenReturnAllDifferentPairs() {
/* Data */
final int[] input = {2, 4, 3, 3, 8};
final int sum = 6;
/* Call service */
final List<Integer> pairs = DifferentPairs.findPairsWithForLoop(input, sum);
/* Check results */
assertThat(pairs).hasSize(2).contains(4,3).doesNotContain(8);
}
@Test
public void whenStreamApi_thenReturnAllDifferentPairs() {
/* Data */
final int[] input = {2, 4, 3, 3, 8};
final int sum = 6;
/* Call service */
final List<Integer> pairs = DifferentPairs.findPairsWithStreamApi(input, sum);
/* Check results */
assertNotNull(pairs);
assertEquals(pairs.size(),2);
assertEquals(pairs.get(0), new Integer(4));
assertThat(pairs).hasSize(2).contains(4,3).doesNotContain(8);
}
}
algorithms/src/test/java/com/baeldung/algorithms/pairsaddupnumber/ExistingPairsUnitTest.java
+34
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@@ -0,0 +1,34 @@
package com.baeldung.algorithms.pairsaddupnumber;
import org.junit.Test;
import java.util.List;
import static org.assertj.core.api.Assertions.assertThat;
public class ExistingPairsUnitTest {
/* All existing pairs */
@Test
public void whenTraditionalLoop_thenReturnAllExistingPairs() {
/* Data */
final int[] input = {2, 4, 3, 3, 8};
final int sum = 6;
/* Call service */
final List<Integer> pairs = ExistingPairs.findPairsWithForLoop(input, sum);
/* Check results */
assertThat(pairs).hasSize(4).contains(2,4,3,3).doesNotContain(8);
}
@Test
public void whenStreamApi_thenReturnAllExistingPairs() {
/* Data */
final int[] input = {2, 4, 3, 3, 8};
final int sum = 6;
/* Call service */
final List<Integer> pairs = ExistingPairs.findPairsWithStreamApi(input, sum);
/* Check results */
assertThat(pairs).hasSize(4).contains(2,4,3,3).doesNotContain(8);
}
}
apache-fop/pom.xml
-36
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@@ -82,42 +82,6 @@
</resources>
</build>
<profiles>
<profile>
<id>integration</id>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<executions>
<execution>
<phase>integration-test</phase>
<goals>
<goal>test</goal>
</goals>
<configuration>
<excludes>
<exclude>**/*ManualTest.java</exclude>
</excludes>
<includes>
<include>**/*IntegrationTest.java</include>
<exclude>**/*LiveTest.java</exclude>
</includes>
</configuration>
</execution>
</executions>
<configuration>
<systemPropertyVariables>
<test.mime>json</test.mime>
</systemPropertyVariables>
</configuration>
</plugin>
</plugins>
</build>
</profile>
</profiles>
<properties>
<fop.version>1.1</fop.version>
<avalon-framework.version>4.3</avalon-framework.version>
apache-poi/README.md
+1 -1
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@@ -1,4 +1,4 @@
### Relevant Articles:
- [Microsoft Word Processing in Java with Apache POI](http://www.baeldung.com/java-microsoft-word-with-apache-poi)
- [Working with Microsoft Excel in Java](http://www.baeldung.com/java-microsoft-excel)
- [Creating a MS PowerPoint Presentation in Java](https://github.com/eugenp/tutorials/tree/master/apache-poi)
- [Creating a MS PowerPoint Presentation in Java](http://www.baeldung.com/apache-poi-slideshow)
aws/src/main/java/com/baeldung/sqs/SQSApplication.java
+146
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@@ -0,0 +1,146 @@
package com.baeldung.sqs;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.AWSStaticCredentialsProvider;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.sqs.AmazonSQSClientBuilder;
import com.amazonaws.services.sqs.model.CreateQueueRequest;
import com.amazonaws.services.sqs.model.DeleteMessageRequest;
import com.amazonaws.services.sqs.model.GetQueueAttributesRequest;
import com.amazonaws.services.sqs.model.GetQueueAttributesResult;
import com.amazonaws.services.sqs.model.MessageAttributeValue;
import com.amazonaws.services.sqs.model.ReceiveMessageRequest;
import com.amazonaws.services.sqs.model.SendMessageBatchRequest;
import com.amazonaws.services.sqs.model.SendMessageRequest;
import com.amazonaws.services.sqs.model.SetQueueAttributesRequest;
import com.amazonaws.services.sqs.model.SendMessageBatchRequestEntry;
import com.amazonaws.services.sqs.model.Message;
import com.amazonaws.services.sqs.AmazonSQS;
public class SQSApplication {
private static final AWSCredentials credentials;
static {
// put your accesskey and secretkey here
credentials = new BasicAWSCredentials(
"<AWS accesskey>",
"<AWS secretkey>"
);
}
public static void main(String[] args) {
// Set up the client
AmazonSQS sqs = AmazonSQSClientBuilder.standard()
.withCredentials(new AWSStaticCredentialsProvider(credentials))
.withRegion(Regions.US_EAST_1)
.build();
// Create a standard queue
CreateQueueRequest createStandardQueueRequest = new CreateQueueRequest("baeldung-queue");
String standardQueueUrl = sqs.createQueue(createStandardQueueRequest)
.getQueueUrl();
System.out.println(standardQueueUrl);
// Create a fifo queue
Map<String, String> queueAttributes = new HashMap<String, String>();
queueAttributes.put("FifoQueue", "true");
queueAttributes.put("ContentBasedDeduplication", "true");
CreateQueueRequest createFifoQueueRequest = new CreateQueueRequest("baeldung-queue.fifo").withAttributes(queueAttributes);
String fifoQueueUrl = sqs.createQueue(createFifoQueueRequest)
.getQueueUrl();
System.out.println(fifoQueueUrl);
// Set up a dead letter queue
String deadLetterQueueUrl = sqs.createQueue("baeldung-dead-letter-queue")
.getQueueUrl();
GetQueueAttributesResult deadLetterQueueAttributes = sqs.getQueueAttributes(new GetQueueAttributesRequest(deadLetterQueueUrl).withAttributeNames("QueueArn"));
String deadLetterQueueARN = deadLetterQueueAttributes.getAttributes()
.get("QueueArn");
SetQueueAttributesRequest queueAttributesRequest = new SetQueueAttributesRequest().withQueueUrl(standardQueueUrl)
.addAttributesEntry("RedrivePolicy", "{\"maxReceiveCount\":\"2\", " + "\"deadLetterTargetArn\":\"" + deadLetterQueueARN + "\"}");
sqs.setQueueAttributes(queueAttributesRequest);
// Send a message to a standard queue
Map<String, MessageAttributeValue> messageAttributes = new HashMap<>();
messageAttributes.put("AttributeOne", new MessageAttributeValue().withStringValue("This is an attribute")
.withDataType("String"));
SendMessageRequest sendMessageStandardQueue = new SendMessageRequest().withQueueUrl(standardQueueUrl)
.withMessageBody("A simple message.")
.withDelaySeconds(30) // Message will arrive in the queue after 30 seconds. We can use this only in standard queues
.withMessageAttributes(messageAttributes);
sqs.sendMessage(sendMessageStandardQueue);
// Send a message to a fifo queue
SendMessageRequest sendMessageFifoQueue = new SendMessageRequest().withQueueUrl(fifoQueueUrl)
.withMessageBody("FIFO Queue")
.withMessageGroupId("baeldung-group-1")
.withMessageAttributes(messageAttributes);
sqs.sendMessage(sendMessageFifoQueue);
// Send multiple messages
List<SendMessageBatchRequestEntry> messageEntries = new ArrayList<>();
messageEntries.add(new SendMessageBatchRequestEntry().withId("id-1")
.withMessageBody("batch-1")
.withMessageGroupId("baeldung-group-1"));
messageEntries.add(new SendMessageBatchRequestEntry().withId("id-2")
.withMessageBody("batch-2")
.withMessageGroupId("baeldung-group-1"));
SendMessageBatchRequest sendMessageBatchRequest = new SendMessageBatchRequest(fifoQueueUrl, messageEntries);
sqs.sendMessageBatch(sendMessageBatchRequest);
// Read a message from a queue
ReceiveMessageRequest receiveMessageRequest = new ReceiveMessageRequest(fifoQueueUrl).withWaitTimeSeconds(10) // Long polling;
.withMaxNumberOfMessages(1); // Max is 10
List<Message> sqsMessages = sqs.receiveMessage(receiveMessageRequest)
.getMessages();
sqsMessages.get(0)
.getAttributes();
sqsMessages.get(0)
.getBody();
// Delete a message from a queue
sqs.deleteMessage(new DeleteMessageRequest().withQueueUrl(fifoQueueUrl)
.withReceiptHandle(sqsMessages.get(0)
.getReceiptHandle()));
// Monitoring
GetQueueAttributesRequest getQueueAttributesRequest = new GetQueueAttributesRequest(standardQueueUrl).withAttributeNames("All");
GetQueueAttributesResult getQueueAttributesResult = sqs.getQueueAttributes(getQueueAttributesRequest);
System.out.println(String.format("The number of messages on the queue: %s", getQueueAttributesResult.getAttributes()
.get("ApproximateNumberOfMessages")));
System.out.println(String.format("The number of messages in flight: %s", getQueueAttributesResult.getAttributes()
.get("ApproximateNumberOfMessagesNotVisible")));
}
}
cdi/pom.xml
+1 -35
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@@ -44,41 +44,7 @@
</dependency>
</dependencies>
<profiles>
<profile>
<id>integration</id>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<executions>
<execution>
<phase>integration-test</phase>
<goals>
<goal>test</goal>
</goals>
<configuration>
<excludes>
<exclude>**/*LiveTest.java</exclude>
</excludes>
<includes>
<include>**/*IntegrationTest.java</include>
</includes>
</configuration>
</execution>
</executions>
<configuration>
<systemPropertyVariables>
<test.mime>json</test.mime>
</systemPropertyVariables>
</configuration>
</plugin>
</plugins>
</build>
</profile>
</profiles>
<properties>
<spring.version>4.3.4.RELEASE</spring.version>
<aspectjweaver.version>1.8.9</aspectjweaver.version>
core-java-8/pom.xml
-35
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@@ -236,41 +236,6 @@
</plugins>
</build>
<profiles>
<profile>
<id>integration</id>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<executions>
<execution>
<phase>integration-test</phase>
<goals>
<goal>test</goal>
</goals>
<configuration>
<excludes>
<exclude>**/*ManualTest.java</exclude>
</excludes>
<includes>
<include>**/*IntegrationTest.java</include>
</includes>
</configuration>
</execution>
</executions>
<configuration>
<systemPropertyVariables>
<test.mime>json</test.mime>
</systemPropertyVariables>
</configuration>
</plugin>
</plugins>
</build>
</profile>
</profiles>
<properties>
core-java-9/README.md
+1
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@@ -22,3 +22,4 @@
- [Java 9 Variable Handles Demistyfied](http://www.baeldung.com/java-variable-handles)
- [Exploring the New HTTP Client in Java 9](http://www.baeldung.com/java-9-http-client)
- [Method Handles in Java](http://www.baeldung.com/java-method-handles)
- [Introduction to Chronicle Queue](http://www.baeldung.com/java-chronicle-queue)
core-java-concurrency/pom.xml
-35
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@@ -183,41 +183,6 @@
</plugins>
</build>
<profiles>
<profile>
<id>integration</id>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<executions>
<execution>
<phase>integration-test</phase>
<goals>
<goal>test</goal>
</goals>
<configuration>
<excludes>
<exclude>**/*ManualTest.java</exclude>
</excludes>
<includes>
<include>**/*IntegrationTest.java</include>
</includes>
</configuration>
</execution>
</executions>
<configuration>
<systemPropertyVariables>
<test.mime>json</test.mime>
</systemPropertyVariables>
</configuration>
</plugin>
</plugins>
</build>
</profile>
</profiles>
<properties>
core-java-io/README.md
+3 -1
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@@ -22,4 +22,6 @@
- [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)
- [Zipping and Unzipping in Java](http://www.baeldung.com/java-compress-and-uncompress)
- [Java NIO2 Path API](http://www.baeldung.com/java-nio-2-path)
- [A Guide to WatchService in Java NIO2](http://www.baeldung.com/java-nio2-watchservice)
core-java/README.md
+2 -1
View File
@@ -151,4 +151,5 @@
- [An Advanced Tagging Implementation with JPA](http://www.baeldung.com/jpa-tagging-advanced)
- [Handling Daylight Savings Time in Java](http://www.baeldung.com/java-daylight-savings)
- [Inheritance and Composition (Is-a vs Has-a relationship) in Java](http://www.baeldung.com/java-inheritance-composition)
- [Finding Max/Min of a List or Collection](http://www.baeldung.com/java-collection-min-max)
- [The "final" Keyword in Java](http://www.baeldung.com/java-final)
core-java/pom.xml
+5
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@@ -235,6 +235,11 @@
<artifactId>h2</artifactId>
<version>1.4.197</version>
</dependency>
<dependency>
<groupId>javax.mail</groupId>
<artifactId>mail</artifactId>
<version>1.5.0-b01</version>
</dependency>
</dependencies>
<build>
core-java/src/main/java/com/baeldung/assertion/Assertion.java
+26
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@@ -0,0 +1,26 @@
package com.baeldung.assertion;
/**
* Simple demonstration of using Java assert keyword.
*/
public class Assertion {
public static void main(String[] args) {
Assertion assertion = new Assertion();
assertion.setup();
}
public void setup() {
Object conn = getConnection();
assert conn != null : "Connection is null";
// continue with other setup ...
}
// Simulate failure to get a connection; using Object
// to avoid dependencies on JDBC or some other heavy
// 3rd party library
public Object getConnection() {
return null;
}
}
core-java/src/main/java/com/baeldung/designpatterns/singleton/synchronization/DclSingleton.java
+38
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@@ -0,0 +1,38 @@
package com.baeldung.designpatterns.singleton.synchronization;
/**
* Double-checked locking design pattern applied to a singleton.
*
* @author Donato Rimenti
*
*/
public class DclSingleton {
/**
* Current instance of the singleton.
*/
private static volatile DclSingleton instance;
/**
* Private constructor to avoid instantiation.
*/
private DclSingleton() {
}
/**
* Returns the current instance of the singleton.
*
* @return the current instance of the singleton
*/
public static DclSingleton getInstance() {
if (instance == null) {
synchronized (DclSingleton.class) {
if (instance == null) {
instance = new DclSingleton();
}
}
}
return instance;
}
}
core-java/src/main/java/com/baeldung/designpatterns/singleton/synchronization/DraconianSingleton.java
+34
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@@ -0,0 +1,34 @@
package com.baeldung.designpatterns.singleton.synchronization;
/**
* Draconian singleton. The method to get the instance is synchronized.
*
* @author Donato Rimenti
*
*/
public class DraconianSingleton {
/**
* Current instance of the singleton.
*/
private static DraconianSingleton instance;
/**
* Private constructor to avoid instantiation.
*/
private DraconianSingleton() {
}
/**
* Returns the current instance of the singleton.
*
* @return the current instance of the singleton
*/
public static synchronized DraconianSingleton getInstance() {
if (instance == null) {
instance = new DraconianSingleton();
}
return instance;
}
}
core-java/src/main/java/com/baeldung/designpatterns/singleton/synchronization/EarlyInitSingleton.java
+31
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package com.baeldung.designpatterns.singleton.synchronization;
/**
* Singleton with early initialization. Inlines the singleton instance
* initialization.
*
* @author Donato Rimenti
*
*/
public class EarlyInitSingleton {
/**
* Current instance of the singleton.
*/
private static final EarlyInitSingleton INSTANCE = new EarlyInitSingleton();
/**
* Private constructor to avoid instantiation.
*/
private EarlyInitSingleton() {
}
/**
* Returns the current instance of the singleton.
*
* @return the current instance of the singleton
*/
public static EarlyInitSingleton getInstance() {
return INSTANCE;
}
}
core-java/src/main/java/com/baeldung/designpatterns/singleton/synchronization/EnumSingleton.java
+16
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package com.baeldung.designpatterns.singleton.synchronization;
/**
* Enum singleton pattern. Uses an enum to hold a reference to the singleton
* instance.
*
* @author Donato Rimenti
*
*/
public enum EnumSingleton {
/**
* Current instance of the singleton.
*/
INSTANCE;
}
core-java/src/main/java/com/baeldung/designpatterns/singleton/synchronization/InitOnDemandSingleton.java
+41
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package com.baeldung.designpatterns.singleton.synchronization;
/**
* Initialization on demand singleton pattern. Uses a nested static class to
* hold a reference to the singleton instance.
*
* @author Donato Rimenti
*
*/
public class InitOnDemandSingleton {
/**
* Holder for a singleton instance.
*
* @author Donato Rimenti
*
*/
private static class InstanceHolder {
/**
* Current instance of the singleton.
*/
private static final InitOnDemandSingleton INSTANCE = new InitOnDemandSingleton();
}
/**
* Private constructor to avoid instantiation.
*/
private InitOnDemandSingleton() {
}
/**
* Returns the current instance of the singleton.
*
* @return the current instance of the singleton
*/
public static InitOnDemandSingleton getInstance() {
return InstanceHolder.INSTANCE;
}
}
core-java/src/main/java/com/baeldung/mail/EmailService.java
+80
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package com.baeldung.mail;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.File;
import java.util.Properties;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;
public class EmailService {
private String host = "";
private int port = 0;
private String username = "";
private String password = "";
public EmailService(String host, int port, String username, String password) {
this.host = host;
this.port = port;
this.username = username;
this.password = password;
sendMail();
}
private void sendMail() {
Properties prop = new Properties();
prop.put("mail.smtp.auth", true);
prop.put("mail.smtp.starttls.enable", "true");
prop.put("mail.smtp.host", host);
prop.put("mail.smtp.port", port);
prop.put("mail.smtp.ssl.trust", host);
Session session = Session.getInstance(prop, new Authenticator() {
@Override
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(username, password);
}
});
try {
Message message = new MimeMessage(session);
message.setFrom(new InternetAddress("[email protected]"));
message.setRecipients(Message.RecipientType.TO, InternetAddress.parse("[email protected]"));
message.setSubject("Mail Subject");
String msg = "This is my first email using JavaMailer";
MimeBodyPart mimeBodyPart = new MimeBodyPart();
mimeBodyPart.setContent(msg, "text/html");
MimeBodyPart attachmentBodyPart = new MimeBodyPart();
attachmentBodyPart.attachFile(new File("pom.xml"));
Multipart multipart = new MimeMultipart();
multipart.addBodyPart(mimeBodyPart);
multipart.addBodyPart(attachmentBodyPart);
message.setContent(multipart);
Transport.send(message);
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String ... args) {
new EmailService("smtp.mailtrap.io", 25, "87ba3d9555fae8", "91cb4379af43ed");
}
}
core-java/src/main/java/com/baeldung/optionalparams/MultiVitamin.java
+50
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package com.baeldung.optionalparams;
public class MultiVitamin {
private String name; // required
private int vitaminA; // in mcg
private int vitaminC; // in mg
private int calcium; // in mg
private int iron; // in mg
public MultiVitamin(String name) {
this.name = name;
}
public String getName() {
return name;
}
public int getVitaminA() {
return vitaminA;
}
public void setVitaminA(int vitaminA) {
this.vitaminA = vitaminA;
}
public int getVitaminC() {
return vitaminC;
}
public void setVitaminC(int vitaminC) {
this.vitaminC = vitaminC;
}
public int getCalcium() {
return calcium;
}
public void setCalcium(int calcium) {
this.calcium = calcium;
}
public int getIron() {
return iron;
}
public void setIron(int iron) {
this.iron = iron;
}
}
core-java/src/main/java/com/baeldung/optionalparams/MultiVitaminAllowingNulls.java
+38
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package com.baeldung.optionalparams;
public class MultiVitaminAllowingNulls {
private String name; // required
private Integer vitaminA; // in mcg
private Integer vitaminC; // in mg
private Integer calcium; // in mg
private Integer iron; // in mg
public MultiVitaminAllowingNulls(String name, Integer vitaminA, Integer vitaminC, Integer calcium, Integer iron) {
this.name = name;
this.vitaminA = vitaminA;
this.vitaminC = vitaminC;
this.calcium = calcium;
this.iron = iron;
}
public String getName() {
return name;
}
public Integer getVitaminA() {
return vitaminA;
}
public Integer getVitaminC() {
return vitaminC;
}
public Integer getCalcium() {
return calcium;
}
public Integer getIron() {
return iron;
}
}
core-java/src/main/java/com/baeldung/optionalparams/MultiVitaminOverloading.java
+56
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package com.baeldung.optionalparams;
public class MultiVitaminOverloading {
static final int DEFAULT_IRON_AMOUNT = 20;
private final String name; // required
private final int vitaminA; // in mcg
private final int vitaminC; // in mg
private final int calcium; // in mg
private final int iron; // in mg
public MultiVitaminOverloading(String name) {
this(name, 0);
}
public MultiVitaminOverloading(String name, int vitaminA) {
this(name, vitaminA, 0);
}
public MultiVitaminOverloading(String name, int vitaminA, int vitaminC) {
this(name, vitaminA, vitaminC, 0);
}
public MultiVitaminOverloading(String name, int vitaminA, int vitaminC, int calcium) {
this(name, vitaminA, vitaminC, calcium, DEFAULT_IRON_AMOUNT);
}
public MultiVitaminOverloading(String name, int vitaminA, int vitaminC, int calcium, int iron) {
this.name = name;
this.vitaminA = vitaminA;
this.vitaminC = vitaminC;
this.calcium = calcium;
this.iron = iron;
}
public String getName() {
return name;
}
public int getVitaminA() {
return vitaminA;
}
public int getVitaminC() {
return vitaminC;
}
public int getCalcium() {
return calcium;
}
public int getIron() {
return iron;
}
}
core-java/src/main/java/com/baeldung/optionalparams/MultiVitaminStaticFactoryMethods.java
+52
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package com.baeldung.optionalparams;
public class MultiVitaminStaticFactoryMethods {
static final int IRON_AMT_DEF = 20;
static final int IRON_AMT_MEN = 30;
static final int CALCIUM_AMT_DEF = 100;
static final int CALCIUM_AMT_WOMEN = 120;
private final String name; // required
private final int vitaminA; // in mcg
private final int vitaminC; // in mg
private final int calcium; // in mg
private final int iron; // in mg
public static MultiVitaminStaticFactoryMethods forMen(String name) {
return new MultiVitaminStaticFactoryMethods(name, 5000, 60, CALCIUM_AMT_DEF, IRON_AMT_MEN);
}
public static MultiVitaminStaticFactoryMethods forWomen(String name) {
return new MultiVitaminStaticFactoryMethods(name, 5000, 60, CALCIUM_AMT_WOMEN, IRON_AMT_DEF);
}
private MultiVitaminStaticFactoryMethods(String name, int vitaminA, int vitaminC, int calcium, int iron) {
this.name = name;
this.vitaminA = vitaminA;
this.vitaminC = vitaminC;
this.calcium = calcium;
this.iron = iron;
}
public String getName() {
return name;
}
public int getVitaminA() {
return vitaminA;
}
public int getVitaminC() {
return vitaminC;
}
public int getCalcium() {
return calcium;
}
public int getIron() {
return iron;
}
}
core-java/src/main/java/com/baeldung/optionalparams/MultiVitaminWithBuilder.java
+77
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package com.baeldung.optionalparams;
public class MultiVitaminWithBuilder {
private final String name; // required
private final int vitaminA; // in mcg
private final int vitaminC; // in mg
private final int calcium; // in mg
private final int iron; // in mg
private MultiVitaminWithBuilder(MultiVitaminBuilder builder) {
this.name = builder.name;
this.vitaminA = builder.vitaminA;
this.vitaminC = builder.vitaminC;
this.calcium = builder.calcium;
this.iron = builder.iron;
}
public String getName() {
return name;
}
public int getVitaminA() {
return vitaminA;
}
public int getVitaminC() {
return vitaminC;
}
public int getCalcium() {
return calcium;
}
public int getIron() {
return iron;
}
public static class MultiVitaminBuilder {
private static final int ZERO = 0;
private final String name; // required
private int vitaminA = ZERO;
private int vitaminC = ZERO;
private int calcium = ZERO;
private int iron = ZERO;
public MultiVitaminBuilder(String name) {
this.name = name;
}
public MultiVitaminBuilder withVitaminA(int vitaminA) {
this.vitaminA = vitaminA;
return this;
}
public MultiVitaminBuilder withVitaminC(int vitaminC) {
this.vitaminC = vitaminC;
return this;
}
public MultiVitaminBuilder withCalcium(int calcium) {
this.calcium = calcium;
return this;
}
public MultiVitaminBuilder withIron(int iron) {
this.iron = iron;
return this;
}
public MultiVitaminWithBuilder build() {
return new MultiVitaminWithBuilder(this);
}
}
}
core-java/src/main/java/com/baeldung/parameterpassing/NonPrimitives.java
+27
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package com.baeldung.parameterpassing;
public class NonPrimitives {
public static void main(String[] args) {
FooClass a = new FooClass(1);
FooClass b = new FooClass(1);
System.out.printf("Before Modification: a = %d and b = %d ", a.num, b.num);
modify(a, b);
System.out.printf("\nAfter Modification: a = %d and b = %d ", a.num, b.num);
}
public static void modify(FooClass a1, FooClass b1) {
a1.num++;
b1 = new FooClass(1);
b1.num++;
}
}
class FooClass {
public int num;
public FooClass(int num) {
this.num = num;
}
}

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