The Runtime class in Java is part of the java.lang package and is a singleton class that provides a way to interface with the Java Virtual Machine (JVM) at runtime. It lets your program interact with the environment, such as memory management, executing system commands, or exiting the program. 🔑 Key Features of Runtime…
The System class in Java is a final class in java.lang package that provides useful system-related utilities. It cannot be instantiated (constructor is private), and all of its members are static. 🔑 Features of System Class Here are the main things you can do with it: 1. Standard Input, Output, Error Streams System.out →…
In Java, both StringBuffer and StringBuilder are classes used to create and manipulate mutable strings (unlike String, which is immutable). Here’s the comparison: 🔑 1. Mutability Both StringBuffer and StringBuilder create mutable string objects (content can be changed without creating new objects). 🔑 2. Thread Safety StringBuffer Thread-safe, because its methods are synchronized. Suitable…
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What is a Replica Set? A replica set is a group of database servers that maintain the same dataset to provide redundancy and high availability. Essentially, it’s a way to make your database fault-tolerant: if one server fails, another can take over with minimal downtime. Key Points: Primary: Receives all write operations. There is…
1. CREATE (Insert Documents) Insert one document: db.collectionName.insertOne({ name: "Alice", age: 25, city: "New York" }); db.collectionName.insertOne({ name: "Alice", age: 25, city: "New York" }); Insert multiple documents: db.collectionName.insertMany([ { name: "Bob", age: 30, city: "Los Angeles" }, { name: "Charlie", age: 28, city: "Chicago" } ]); db.collectionName.insertMany([ { name: "Bob", age: 30, city:…
1. Version Control in Databases Just like version control for code (Git, for example), database version control is a way to track and manage changes to your database schema over time. Instead of manually updating databases on different environments, version control helps keep track of what changed, when, and why. Why it’s important: Multiple…
1. What is a Cursor? A cursor is a database object used to retrieve, traverse, and manipulate one row at a time from the result set of a query. Unlike a normal SELECT query that returns all rows at once, a cursor allows you to process rows individually. This is especially useful when you…
In SQL, CASCADE is an option used with FOREIGN KEY constraints when defining relationships between tables. It specifies that certain actions on a parent table should automatically propagate to the related child table(s). The most common use cases are ON DELETE CASCADE and ON UPDATE CASCADE. Let's break it down: 1. ON DELETE CASCADE…