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 Here's how you can configure the Javalin instance to create an HTTP GET endpoint at http://localhost:9000/hello that returns the string "Hello World" in the response: java Copy code import io.javalin.Javalin; public class JavalinSingleton { /** * Using the app.get method, Create an HTTP GET endpoint at the url: http://localhost:9000/hello that will * return the string "Hello World" in the response. * * You will not need to run app.start in this method. The test cases, or main method, will do this for you - this * method only needs to return a properly configured Javalin Server, represented by the 'app' object created below. * * Note: Please refer to the "CreatingEndpoints.MD" file for more assistance if needed. */ public static Javalin getInstance () { Javalin app = Javalin.create(); // Define the HTTP GET endpoint app.get( "/hello" , c...

 java JDBC Java Database Connectivity (JDBC) is an API for connecting and executing queries with databases in Java. It provides methods for querying and updating data in a database and is oriented towards relational databases. Here's a quick overview of what you can do with JDBC: Establishing a Connection : You can connect to a database using the DriverManager class and a database URL. Creating Statements : You can use the Statement or PreparedStatement classes to execute SQL queries. Executing Queries : You can retrieve data from a database using the ResultSet class. Updating Data : You can insert, update, and delete data in a database. Handling Transactions : You can manage transactions to ensure data integrity. Here's a basic example of how to connect to a database and execute a simple query: java import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; public class JDBCDemo { public static void main ...

Below are a range of Kubernetes interview questions categorized from basic to advanced levels. These questions will test a candidate's knowledge of Kubernetes, its architecture, components, and how to use it effectively for container orchestration. ### **Basic Kubernetes Interview Questions** 1. **What is Kubernetes?**    - Explain what Kubernetes is and what problem it solves. 2. **What are the key components of Kubernetes?**    - Answer should include nodes, pods, clusters, kube-apiserver, kube-scheduler, etcd, kube-controller-manager, and kubelet. 3. **What is a Pod in Kubernetes?**    - Define what a Pod is, how it differs from a container, and why it's important in Kubernetes. 4. **What is the role of the kube-apiserver?**    - Describe the role of the Kubernetes API server in the control plane. 5. **What is a Kubernetes Node?**    - Explain what a node is, the different types (master and worker), and the role it plays in a Kubernet...

An example of a **simple Jenkins CI/CD pipeline** that you can use for learning purposes. The pipeline will cover the following stages: 1. **Checkout**: Pull the latest code from a Git repository. 2. **Build**: Build the application (for example, a Java project using Maven). 3. **Test**: Run unit tests. 4. **Deploy**: Deploy the application to a staging server (this can be a simple script for now). 5. **Post actions**: Notify the team about the success or failure of the pipeline. We'll also go through the steps to configure Jenkins for this pipeline. --- ### **Step 1: Install Jenkins (if not already installed)** If you haven't already installed Jenkins, follow these steps: #### On Ubuntu: ```bash sudo apt update sudo apt install openjdk-11-jdk sudo apt install wget wget -q -O - https://pkg.jenkins.io/debian/jenkins.io.key | sudo apt-key add - sudo sh -c 'echo deb http://pkg.jenkins.io/debian/jenkins.io/ stable main > /etc/apt/sources.list.d/jenkins.list' sudo apt upd...

 Here's an SQL query to create a simple table with columns for userid , username , and email : sql Copy code CREATE TABLE users ( userid INT AUTO_INCREMENT PRIMARY KEY, -- Automatically increments the user ID username VARCHAR ( 255 ) NOT NULL , -- Username cannot be NULL email VARCHAR ( 255 ) NOT NULL , -- Email cannot be NULL UNIQUE (email) -- Ensure email is unique ); Explanation: userid INT AUTO_INCREMENT PRIMARY KEY : The userid column is of type INT and is set to automatically increment (so each new user gets a unique ID). This also makes it the primary key of the table, ensuring each userid is unique. username VARCHAR(255) NOT NULL : The username is a string (up to 255 characters), and it cannot be NULL . email VARCHAR(255) NOT NULL : The email is also a string (up to 255 characters), and it cannot be NULL . UNIQUE(email) : This ensures that each email in the table is unique. No two users can have the...

SELECT NAME FROM CITY WHERE POPULATION>120000 AND COUNTRYCODE='USA'; SELECT * FROM CITY; SELECT * FROM city WHERE COUNTRYCODE='JPN'; SELECT NAME FROM CITY WHERE COUNTRYCODE='JPN'; SELECT DISTINCT CITY FROM STATION WHERE (ID%2)=0;

Continuous Integration (CI) and Continuous Delivery/Deployment (CD) are key practices in modern software development that aim to automate the process of integrating code changes and delivering those changes to production environments. Jenkins is one of the most popular tools for setting up CI/CD pipelines. Here's a step-by-step guide to learning CI/CD with Jenkins: Step 1: Understanding the Basics of CI/CD Continuous Integration (CI): Involves automatically testing and integrating code changes into a shared repository, ensuring that code is always in a deployable state. Continuous Delivery/Deployment (CD): Focuses on automatically pushing code changes to production after successful testing, with continuous delivery allowing manual approval and continuous deployment doing it automatically. Step 2: Setting Up Jenkins 1. Install Jenkins Linux (Ubuntu/Debian): bash Copy code sudo apt update sudo apt install openjdk-11-jdk sudo apt install wget wget -q -O - https://pkg.jenkins.io/debi...