🏗️ Java System Design With Code: Building Scalable Systems Made Simple

This content originally appeared on DEV Community and was authored by FullStackPrep.Dev

Java System Design With Code: Building Scalable Systems Made Simple

When interviewers ask you system design questions in Java, they’re not just testing syntax—they want to know if you can think like an architect.

But don’t worry: with the right patterns, examples, and mindset, system design in Java becomes much less intimidating.

Why System Design Matters

Companies like Amazon, Google, and Netflix want developers who can design systems that scale.

Writing code is one thing—but designing how components interact is the real test.

Good design = performance, reliability, and maintainability.

Key Principles

1. Scalability – Can the system handle 1 user… or 1 million?

2. Fault Tolerance – If part of the system fails, does the rest keep running?

3. Readability – Clean, modular code that others can understand.

4. Extensibility – Easy to add new features later.

Example: Designing a Simple URL Shortener

Imagine building a Java-based URL shortener (like Bitly).

Requirement: Convert long URLs into short ones.

Approach:

Use Hashing or Base62 encoding for unique IDs.

Store mapping in a database (MySQL/NoSQL).

Implement caching (e.g., Redis) for faster reads.

Java Code Snippet

import java.util.HashMap;

public class UrlShortener {
private HashMap map = new HashMap<>();
private static final String BASE = “http://short.ly/“;

public String shorten(String longUrl) {
    String key = Integer.toHexString(longUrl.hashCode());
    map.put(key, longUrl);
    return BASE + key;
}

public String expand(String shortUrl) {
    String key = shortUrl.replace(BASE, "");
    return map.getOrDefault(key, "URL not found");
}

}

Patterns to Know for Interviews

Singleton → For global resources like DB connections.

Factory → For object creation flexibility.

Observer → For event-driven systems.

Builder → For constructing complex objects step by step.

Full System Design Guide

I’ve written a detailed breakdown of Java system design with examples and code snippets here
Java System Design With Code

Final Thoughts

System design is where Java knowledge meets real-world application.
Whether it’s designing a URL shortener, chat app, or e-commerce system—knowing the right patterns and principles makes all the difference in interviews.

Originally published via AnalogyAndMe.com

This content originally appeared on DEV Community and was authored by FullStackPrep.Dev