In this tutorial, you will learn about Unit Testing AWS Lambda Function with Java. First, we will have a quick overview of Unit Testing. Then we will look at the required dependencies in order to do Unit Testing of AWS Lambda Function. After that, we will dive deep into the annotations that will be used…
Read More Unit Testing AWS Lambda Function with Javasynchronized void method() {} public class SynchronizedInstanceMethodExample implements Runnable { public static void main(String[] args) { SynchronizedInstanceMethodExample runnable = new SynchronizedInstanceMethodExample(); new Thread(runnable).start(); // creates one thread new Thread(runnable).start(); // creates second thread } // Inherited run method from the Runnable interface @Override public void run() { try { // Calling the non-synchronized method print()…
Read More Java Synchronized Blocks and MethodsIn this guide, you will learn to use @RepeatedTest and @ParametrizedTest annotations introduced in JUnit 5. We’ll look at the capability that lets us run a test a certain number of times. We’ll also look at interfaces that will allow us to retrieve information about the repeated tests. Moreover, we will also look at a…
Read More A Guide to @RepeatedTest and @ParametrizedTest in JUnit 5class PrintArrayElementsExample { public static void main(String[] args) { int[] arr1 = {1, 7, 9, 5, 2, 8, 3}; String[] arr2 = {“Megan”, “Tom”, “Melissa”, “John”, “Steve”}; // print elements of the arr1 System.out.println(Arrays.toString(arr1)); // print elements of the arr2 System.out.println(Arrays.toString(arr2)); } } Output: [1, 7, 9, 5, 2, 8, 3] [Megan, Tom, Melissa, John,…
Read More Print Array Elements in Javapublic class SplitString { public static void main(String[] args) { String names = “Tom,Steve,John,Megan,Melissa”; // split string String[] arr = names.split(“,”); // print the size of the array System.out.println(arr.length); // print the elements Stream.of(arr).forEach(System.out::println); } } Output: 5 Tom Steve John Megan Melissa If you need a list, instead of an array, use the…
Read More Split a comma-separated String in JavaIn this tutorial, you will learn how to secure access to User’s Data in RDS using Lambda Authorizer. First, the Lambda Authorizer function will authenticate the caller by validating JWT using nimbus-jose-jwt library. After that, the Lambda Authorizer function will return an output object containing an IAM policy. The Authorizer will also return additional information…
Read More Lambda Authorizer – Secure Access to User’s Data in RDSIn this tutorial, you will learn how to implement the API Gateway Lambda Authorizer in Java. You will also learn how to make Lambda Authorizer validate Authorization JWT. First, we will create an API using API Gateway then we will make lambda function as an integration point for the GET method of our resource. After…
Read More API Gateway Lambda Authorizer Example in JavaIn this article, you will learn about RabbitMQ and explore its common use cases. I will also guide you step-by-step on how to implement messaging using RabbitMQ in a Spring Boot application. By the end of this article, you will know how to publish and consume messages in a queue. So let’s get started! What…
Read More Messaging with RabbitMQ in Spring Boot Applicationclass BreakOutOfLoop { public static void main(String[] args) { int[] arr = {1, 2, 3, 4, 5}; // iterate over array for (int i = 0; i < arr.length; i++) { if (arr[i] == 3) { // break out of the loop if the current value is equals to 3 System.out.println(“Breaking out of the loop!”);…
Read More How to break out of the loop in Java?class CheckIfArrayContainsValue { public static void main(String[] args) { String[] programmingLanguages = {“Python”, “Kotlin”, “Ruby”, “JavaScript”, “C#”, “Java”, “Flutter”}; for (String lang : programmingLanguages) { if (lang.equals(“Java”)) { System.out.println(“It does contain!”); break; // value found, exit the loop } } } } Output: It does contain! Here, we are iterating over the array, and…
Read More Check if Array Contains a Value in JavaOutput: Some String Here, we put the creation of the Scanner object into a try-with-resources because we want to close the Scanner after it reads all the data. We passed the “\\A” to tell the Scanner to read the entire input stream. import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.nio.charset.StandardCharsets; class ConvertInputStreamToString { /** *…
Read More Convert InputStream to a String in JavaIn this tutorial, we will explore different methods to find duplicate elements in a Java array, including using nested loops, sets, streams, and hash tables. We will also discuss the time and space complexity of each method, so you can choose the most efficient one for your specific use case. Whether you’re a beginner or…
Read More How to Find Duplicate Elements in a Java Arrayclass EscapeDoubleQuotesInString { public static void main(String[] args) { String str = “Hello, I’m \”Steve\” and I am \”Java\” developer”; System.out.println(str); } } Output: Hello, I’m “Steve” and I am “Java” developer Escape double quotes in a JSON object in Java There are many cases where you might need to escape double quotes. In this…
Read More Escape Double Quotes in Java String<dependency> <groupid>org.apache.poi</groupid> <artifactid>poi-ooxml</artifactid> <version>5.0.0</version> </dependency> If you are not familiar with Maven, you can check out this tutorial: Create Java Project with Maven. import lombok.AllArgsConstructor; import lombok.Builder; import lombok.Data; import lombok.NoArgsConstructor; @Data @AllArgsConstructor @NoArgsConstructor public class Product { private int id; private String color; private String size; private int cost; private String description; } import org.apache.poi.ss.usermodel.Cell;…
Read More Read and write Excel files in Java<dependency> <groupid>io.projectreactor</groupid> <artifactid>reactor-test</artifactid> <version>3.1.0.RELEASE</version> <scope>test</scope> </dependency> class ReactiveJavaTutorialTest { @Test public void testFlux() { //Create a Flux Flux <Integer> fluxToTest = Flux.just(1, 2, 3, 4, 5); // Create a test StepVerifier.create(fluxToTest) .expectNext(1) .expectNext(2) .expectNext(3) .expectNext(4) .expectNext(5) .expectComplete() // we expect Flux to complete after sending the number 5 which is the last element .verify(); }…
Read More Testing with StepVerifier in Project Reactor