🔹 1️⃣ String.trim() The classic method for removing whitespace from both ends of a string. Syntax: String trimmed = str.trim(); String trimmed = str.trim(); Behavior: Removes leading and trailing whitespace. Whitespace includes:spaces (' '), tabs ('\t'), newlines ('\n'), carriage returns ('\r'). ✅ Example: String s = " Hello World! "; System.out.println(s.trim()); String s =…
🔹 1️⃣ What Is a Static Block? A static block (also called a static initializer) is a block of code inside a class that is executed when the class is loaded into memory. Runs only once, regardless of how many objects you create. Can be used to initialize static variables or perform class-level setup.…
In Java, asynchronous methods are methods that start a task and return immediately, allowing the program to continue executing without waiting for the task to finish. This is useful for I/O operations, network calls, or long-running computations. Java provides several ways to implement asynchronous methods. 1️⃣ Using CompletableFuture (Java 8+) The modern and recommended…
Sorting a list of strings in Java is straightforward — and you can do it in several ways, depending on whether you want natural order, reverse order, or a custom comparator. Here’s a complete guide 👇 ✅ 1. Sort in Natural (Alphabetical) Order import java.util.*; public class SortStringsExample { public static void main(String[] args)…
In Java, the volatile keyword is used to indicate that a variable’s value may be changed by multiple threads, and that all threads should always see the most up-to-date value of that variable. It’s a key concept in multithreading and concurrency. 🧠 Definition A volatile variable is one whose reads and writes go directly…
In JUnit (Java Unit Testing framework), annotations are special markers (prefixed with @) that tell JUnit how to run and organize your tests. Let’s go over the most important JUnit annotations — for both JUnit 4 and JUnit 5 (Jupiter). 🧪 JUnit 5 (current standard) JUnit 5 annotations come from the package: import org.junit.jupiter.api.*;…
🧠 What is EXISTS? EXISTS is a logical operator in SQL that checks whether a subquery returns any rows. If the subquery returns at least one row, EXISTS evaluates to TRUE. If the subquery returns no rows, EXISTS evaluates to FALSE. It’s often used in a WHERE clause to test for the existence of…
Here’s a comprehensive guide to Docker container commands with explanations and examples. I’ll organize them by category so it’s easy to reference. 1. Running Containers CommandPurposeExampledocker run <image>Run a container from an imagedocker run nginxdocker run -d <image>Run container in detached mode (background)docker run -d nginxdocker run -it <image>Run container interactively with terminaldocker run…
Here’s a comprehensive list of Docker commands related to images, broken down by category, with explanations and examples: 1. Pulling and Searching Images CommandPurposeExampledocker pull <image>Download an image from a registry (e.g., Docker Hub)docker pull nginx:latestdocker search <image>Search for an image in Docker Hubdocker search postgres 2. Listing Images CommandPurposeExampledocker images or docker image…
A Secret in Kubernetes is an object that stores sensitive information such as passwords, tokens, SSH keys, or certificates, separate from application code. Unlike ConfigMaps, Secrets are intended for confidential data and can be handled more securely. ⚙️ Definition A Secret allows you to inject sensitive data into Pods without exposing it in container…