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C# vs Java - Which Language Should You Choose in 2025

#csharp #dotnet

Our team evaluated backend technologies for a new microservices platform. Java advocates cited cross-platform portability and massive ecosystem. C# supporters emphasized modern language features and Azure integration. Both made valid points. Neither told the whole story.

Here's the honest comparison based on 2025 data.

What Are the Main Differences Between C# and Java?

Platform origins:

  • Java: "Write once, run anywhere" philosophy, JVM-based, cross-platform from day one
  • C#: Born Windows-centric, evolved to cross-platform with .NET Core/.NET 10

Current state (2025):

// C# 14 (.NET 10) - Extension properties
public static class StringExtensions
{
    public static bool IsEmail(this string str) =>
        str.Contains("@") && str.Contains(".");
}

var email = "test@example.com";
Console.WriteLine(email.IsEmail()); // true
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// Java 23 - Primitive type patterns
Object obj = 42;
switch (obj) {
    case int i -> System.out.println("Integer: " + i);
    case String s -> System.out.println("String: " + s);
    default -> System.out.println("Other");
}
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Both are mature, enterprise-grade languages with modern features.

How Do C# and Java Compare in Performance?

Benchmarks show near-identical performance for most tasks:

// C# - Binary tree benchmark
var tree = new TreeNode(iterations);
tree.ItemCheck(); // ~2.3 seconds
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// Java - Same benchmark
TreeNode tree = new TreeNode(iterations);
tree.itemCheck(); // ~2.4 seconds
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Real-world performance:

  • C# has a slight edge on Windows (5-15% faster) due to .NET runtime optimizations
  • Java performs consistently across all platforms (JVM maturity)
  • Both compile to intermediate bytecode (IL vs bytecode), then JIT compile to native

New in 2025:

  • C# .NET 10: Native AOT compilation produces single-file executables, faster startup (~50ms vs ~500ms)
  • Java 23: Generational ZGC enabled by default, reduced garbage collection pauses

For most applications, performance differences are negligible. Your code quality matters more than the language choice.

What's the Market Share?

TIOBE Index (June 2025):

  • Java: 4th place, 8.4% rating
  • C#: 5th place, 6.65% rating

GitHub Activity (2024-2025):

  • Java: 4th most-used language
  • C#: 5th most-used language

Java has larger market share, but both are top-tier languages with strong demand.

Which Platforms Do They Support?

Java 23:

  • All major operating systems (Windows, macOS, Linux)
  • Android (native language for mobile apps)
  • Embedded systems
  • Cloud platforms (AWS, Google Cloud, Azure) 
// Java - Truly platform-independent
public class Main {
    public static void main(String[] args) {
        System.out.println("Runs anywhere with JVM");
    }
}
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C# 14 / .NET 10:

  • Windows (native integration, best performance)
  • macOS (full support via .NET 10)
  • Linux (excellent support, widely used in containers)
  • iOS/Android (via .NET MAUI)
  • WebAssembly (via Blazor)
  • Xbox, PlayStation (game development) 
// C# - Cross-platform with .NET 10
Console.WriteLine("Runs on Windows, macOS, Linux");
// Same binary works everywhere (since .NET Core)
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Key difference: Java achieved cross-platform earlier and has deeper Android integration. C# started Windows-only but is now fully cross-platform with stronger game development support (Unity, Unreal).

How Do the Ecosystems Compare?

Java strengths:

  • Enterprise: Spring Boot, Jakarta EE, Hibernate
  • Android development: Native Android SDK
  • Big data: Apache Hadoop, Spark, Kafka
  • Microservices: Spring Cloud, Micronaut, Quarkus
  • Legacy systems: Decades of production code 
// Spring Boot - Java's dominant web framework
@RestController
public class HelloController {
    @GetMapping("/api/hello")
    public String hello() {
        return "Hello from Spring Boot";
    }
}
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C# strengths:

  • Microsoft ecosystem: Azure, Visual Studio, SQL Server
  • Game development: Unity (90% of mobile games), Unreal Engine
  • Desktop applications: WPF, WinForms, .NET MAUI
  • Web development: ASP.NET Core (fastest web framework in TechEmpower benchmarks)
  • Document processing: IronPDF, Office automation 
// ASP.NET Core - Minimal API
var app = WebApplication.Create();

app.MapGet("/api/hello", () => "Hello from ASP.NET Core");

app.Run();
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Both have:

  • Mature ORMs (Entity Framework vs Hibernate)
  • Excellent testing frameworks (xUnit/NUnit vs JUnit/TestNG)
  • Strong dependency injection
  • Package managers (NuGet vs Maven/Gradle)

What Are the Syntax Differences?

Properties:

// C# - First-class properties
public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}

var person = new Person { Name = "Alice", Age = 30 };
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// Java - Manual getters/setters (or use Lombok)
public class Person {
    private String name;
    private int age;

    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public int getAge() { return age; }
    public void setAge(int age) { this.age = age; }
}
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C# has built-in property syntax. Java requires boilerplate (unless using Lombok).

LINQ vs Streams:

// C# - LINQ (Language Integrated Query)
var adults = people
    .Where(p => p.Age >= 18)
    .OrderBy(p => p.Name)
    .Select(p => p.Name)
    .ToList();
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// Java - Streams API
List<String> adults = people.stream()
    .filter(p -> p.getAge() >= 18)
    .sorted(Comparator.comparing(Person::getName))
    .map(Person::getName)
    .collect(Collectors.toList());
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Similar functionality. C#'s LINQ syntax is slightly cleaner.

Async/Await:

// C# - async/await (since C# 5, 2012)
public async Task<string> FetchDataAsync()
{
    using var client = new HttpClient();
    return await client.GetStringAsync("https://api.example.com");
}
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// Java - CompletableFuture (more verbose)
public CompletableFuture<String> fetchData() {
    return CompletableFuture.supplyAsync(() -> {
        // HTTP request code
        return "data";
    });
}
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C# has more elegant async syntax. Java's async requires more ceremony.

What Are the New Features in 2025?

C# 14 (November 2025):

  • Extension properties: Extend types with properties, not just methods
  • Field keyword: Access property backing fields directly
  • Null-conditional assignment: customer?.Name = "Alice";
  • First-class spans: Better memory efficiency 
// C# 14 - Field keyword
public string Name
{
    get => field;
    set => field = value?.Trim(); // Access backing field
}
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Java 23 (September 2025):

  • Primitive type patterns: Pattern matching for primitives
  • Stream Gatherers: Custom intermediate stream operations
  • Generational ZGC: Faster garbage collection by default
  • Vector API improvements: Better SIMD performance 
// Java 23 - Primitive patterns
switch (value) {
    case int i -> process(i);
    case long l -> process(l);
    default -> handleOther();
}
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Both languages are actively evolving. C# focuses on developer productivity and syntax sugar. Java emphasizes performance and runtime improvements.

When Should You Choose Java?

Android development:

// Java is the primary language for Android
public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}
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Native Android SDK. Kotlin is also popular, but Java remains dominant.

Enterprise with existing Java infrastructure:

  • Spring Boot microservices
  • Apache ecosystem (Kafka, Hadoop, Spark)
  • Legacy Java applications
  • JVM-based polyglot environments (Java, Kotlin, Scala)

Cross-platform from day one:

  • Need guaranteed behavior across all operating systems
  • Deploying to diverse server environments
  • Long-term application support (JVM stability)

When platform independence is critical:

  • SaaS products serving diverse customers
  • Applications with unpredictable deployment targets
  • Educational software (runs on any school's computers)

I use Java for Android apps and when interfacing with Java-heavy ecosystems like Kafka.

When Should You Choose C#?

Game development:

// Unity (C# is the primary language)
void Update()
{
    transform.Rotate(Vector3.up * Time.deltaTime * 50f);
}
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Unity powers:

  • 90% of mobile games
  • VR/AR experiences
  • Indie games (Hollow Knight, Cuphead, Among Us)

Microsoft ecosystem projects:

  • Azure cloud services
  • Windows desktop applications
  • Microsoft 365 integrations
  • SQL Server database projects

High-performance web APIs:

// ASP.NET Core - Handles 7M+ requests/sec
app.MapGet("/", () => "Hello World");
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ASP.NET Core ranks #1 in TechEmpower web framework benchmarks.

PDF and document processing:

using IronPdf;
// Install via NuGet: Install-Package IronPdf

var renderer = new [ChromePdfRenderer](https://ironpdf.com/blog/videos/how-to-render-webgl-sites-to-pdf-in-csharp-ironpdf/)();
var pdf = renderer.RenderHtmlAsPdf("<h1>Invoice #12345</h1>");
pdf.SaveAs("invoice.pdf");
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C# has superior document processing libraries (IronPDF, Office interop).

Desktop applications:

  • WPF (rich Windows applications)
  • .NET MAUI (cross-platform mobile/desktop)
  • Avalonia (modern cross-platform UI)

I use C# for web APIs, desktop apps, and any project involving PDFs or Office automation.

How Do IDEs Compare?

Java IDEs:

  • IntelliJ IDEA: Industry standard, excellent refactoring, $249/year
  • Eclipse: Free, mature, large plugin ecosystem
  • NetBeans: Free, good for beginners
  • VS Code: Lightweight, with Java extensions

C# IDEs:

  • Visual Studio 2026: Best C# experience, free Community edition
  • JetBrains Rider: Cross-platform, excellent, $149/year
  • VS Code: Good with C# Dev Kit extension

Winner: Visual Studio for C# is superior to any Java IDE. IntelliJ IDEA for Java is excellent but requires a paid license for full features.

What About Salaries?

Average salaries (USA, 2025):

  • Java developers: $110k-145k
  • C# developers: $110k-140k

Nearly identical. Both are enterprise languages with strong compensation.

Job availability:

  • Java: More positions overall (larger market share)
  • C#: Strong in .NET shops, Microsoft partners, game studios

Both have excellent career prospects.

Which Has Better Learning Curve?

Java:

  • More verbose (getters/setters, exception handling)
  • Stricter conventions
  • Excellent documentation and learning resources
  • Huge community (decades of Stack Overflow answers)

C#:

  • More modern syntax (properties, LINQ, async/await)
  • Steeper initial tooling setup (Visual Studio is large)
  • Smaller but active community
  • Excellent official documentation (Microsoft Learn)

Learning time to productivity:

  • Java: 4-8 weeks
  • C#: 4-8 weeks

Both have similar learning curves for developers with programming experience.

Can You Use Both?

Yes! Common patterns:

Java for backend microservices:

@RestController
public class OrderService {
    // Spring Boot microservice
}
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C# for desktop client:

// WPF desktop app consuming Java API
var client = new HttpClient();
var orders = await client.GetFromJsonAsync<Order[]>("/api/orders");
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Many organizations use Java for server-side services and C# for Windows clients, Unity games, or internal tools.

Which Should You Learn First?

Choose Java if you:

  • Want to develop Android apps
  • Work in enterprise with Java infrastructure
  • Value cross-platform portability above all
  • Prefer established, conservative technology

Choose C# if you:

  • Interested in game development (Unity)
  • Work in Microsoft ecosystem
  • Want modern language features
  • Build Windows desktop applications
  • Need PDF/Office document processing

Pro tip: Learn one well, then learn the other. The concepts transfer easily. I switch between them regularly.

My Recommendation

For 2025:

  1. Learn C# first if you're interested in:

    • Game development
    • Windows apps
    • Modern web APIs
    • Document processing

  2. Learn Java first if you're targeting:

    • Android development
    • Large enterprise environments
    • Big data / Kafka ecosystem
    • Maximum cross-platform portability

Both are excellent languages. Neither is "better" universally. Your choice should depend on your career goals and target platforms.

Reality check: Most senior developers know both. The syntax is similar enough that switching takes days, not months.

Written by Jacob Mellor, CTO at Iron Software. Jacob created IronPDF and leads a team of 50+ engineers building .NET document processing libraries.

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