Java vs C#: A Practical Comparison for Developers

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Java vs C# programming language comparison

Java and C# are more alike than different. Microsoft created C# in 2000 as part of its .NET initiative, and the language borrowed heavily from Java’s design. Both are statically-typed, object-oriented, garbage-collected languages that compile to intermediate bytecode. Developers who know one can learn the other quickly.

The real differences lie in their ecosystems, platform support, and the companies behind them. This comparison helps you understand where each language fits and which might suit your goals.

Origins and Ownership

Sun Microsystems released Java in 1995. Oracle acquired Sun in 2010 and now controls Java’s development. The language is governed by the Java Community Process, which involves multiple companies and individuals. OpenJDK provides a free, open-source implementation.

Microsoft released C# in 2000 alongside the .NET Framework. Anders Hejlsberg, who previously designed Turbo Pascal and Delphi, led the language’s creation. Microsoft controls C#’s evolution, though .NET is now open source and runs on multiple platforms.

The ownership difference matters. Java’s multi-vendor governance means slower, more conservative evolution. C# moves faster because Microsoft can push changes without lengthy committee processes. C# has added features like async/await, pattern matching, and records years before Java equivalents appeared.

Platform and Runtime

Java code compiles to bytecode that runs on the Java Virtual Machine (JVM). The JVM exists for Windows, macOS, Linux, and many other platforms. “Write once, run anywhere” was Java’s founding promise, and it largely delivers. The same .jar file runs on any system with a compatible JVM.

C# code compiles to Common Intermediate Language (CIL) that runs on the Common Language Runtime (CLR). Historically, this meant Windows only. That changed dramatically with .NET Core (2016) and .NET 5+ (2020), which run on Windows, macOS, and Linux. Modern C# is genuinely cross-platform.

For server-side development, both languages now run anywhere. For desktop applications, C# with Windows Presentation Foundation (WPF) or Windows Forms remains Windows-only, while Java’s Swing and JavaFX work cross-platform. For mobile, Java dominates Android while C# powers Xamarin and .NET MAUI for cross-platform mobile development.

Syntax Comparison

The languages look remarkably similar. Both use C-style syntax with curly braces, semicolons, and similar keywords.

A simple class in Java:

public class Person {
    private String name;
    private int age;
    
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    
    public int getAge() {
        return age;
    }
}

The equivalent in C#:

public class Person
{
    public string Name { get; set; }
    public int Age { get; }
    
    public Person(string name, int age)
    {
        Name = name;
        Age = age;
    }
}

C# is more concise here. Properties with automatic getters and setters eliminate boilerplate. Java developers write (or generate) getter and setter methods manually, though newer Java versions offer records for simple data classes.

Properties vs Getters/Setters

C# has first-class property support:

public class Product
{
    public string Name { get; set; }
    public decimal Price { get; private set; }
    
    public decimal PriceWithTax
    {
        get { return Price * 1.1m; }
    }
}

Java uses the getter/setter convention:

public class Product {
    private String name;
    private BigDecimal price;
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    
    public BigDecimal getPrice() {
        return price;
    }
    
    public BigDecimal getPriceWithTax() {
        return price.multiply(new BigDecimal("1.1"));
    }
}

C#’s properties are syntactic sugar, but they reduce code significantly. Java developers often use IDE generation or libraries like Lombok to compensate.

Null Handling

Null reference exceptions plague both languages, but C# added nullable reference types in C# 8.0. When enabled, the compiler warns about potential null dereferences:

string? nullableName = null;     // Explicitly nullable
string nonNullName = "Alice";    // Compiler warns if you assign null

if (nullableName != null)
{
    Console.WriteLine(nullableName.Length);  // Safe
}

Java’s approach relies on Optional for return types and annotations like @Nullable and @NonNull, but enforcement is weaker:

Optional<String> maybeName = Optional.ofNullable(getName());

maybeName.ifPresent(name -> System.out.println(name.length()));

Neither solution eliminates null problems entirely, but C#’s compiler integration catches more issues at build time.

Async Programming

C# introduced async/await in 2012 with C# 5.0. It transformed asynchronous programming from callback complexity into readable sequential code:

public async Task<string> FetchDataAsync(string url)
{
    using var client = new HttpClient();
    string content = await client.GetStringAsync(url);
    return content;
}

Java added similar functionality much later. CompletableFuture arrived in Java 8 (2014), but without language-level async/await:

public CompletableFuture<String> fetchDataAsync(String url) {
    return CompletableFuture.supplyAsync(() -> {
        // HTTP call here
        return content;
    });
}

Java 21 introduced virtual threads (Project Loom), which take a different approach. Instead of async/await syntax, virtual threads let you write blocking code that scales like asynchronous code:

try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
    executor.submit(() -> {
        String content = httpClient.send(request, BodyHandlers.ofString()).body();
        return content;
    });
}

Both approaches work. C#’s async/await is more mature and widely adopted. Java’s virtual threads are newer but arguably simpler since you write normal blocking code.

Generics

Both languages support generics, but implementations differ significantly.

Java uses type erasure. Generic type information exists at compile time but disappears at runtime:

List<String> strings = new ArrayList<>();
List<Integer> integers = new ArrayList<>();

// At runtime, both are just ArrayList
System.out.println(strings.getClass() == integers.getClass());  // true

C# uses reified generics. Type information is preserved at runtime:

List<string> strings = new List<string>();
List<int> integers = new List<int>();

// At runtime, these are different types
Console.WriteLine(strings.GetType() == integers.GetType());  // false

Reified generics enable things Java can’t do: creating instances of generic types, checking generic types at runtime, and using primitive types directly in generics. Java’s erasure was a backward-compatibility compromise that still causes headaches.

Value Types

C# distinguishes between reference types (classes) and value types (structs):

public struct Point
{
    public int X { get; }
    public int Y { get; }
    
    public Point(int x, int y)
    {
        X = x;
        Y = y;
    }
}

Structs are stored on the stack (when used as local variables), avoid heap allocation, and are copied by value. This improves performance for small, frequently-used data structures.

Java has only primitives (int, double, boolean, etc.) and reference types. Everything else lives on the heap. Project Valhalla aims to bring value types to Java, but it’s been in development for years.

LINQ vs Streams

C#’s Language Integrated Query (LINQ) provides powerful data querying:

var results = people
    .Where(p => p.Age >= 18)
    .OrderBy(p => p.Name)
    .Select(p => p.Name.ToUpper())
    .ToList();

Java’s Stream API offers similar functionality:

List<String> results = people.stream()
    .filter(p -> p.getAge() >= 18)
    .sorted(Comparator.comparing(Person::getName))
    .map(p -> p.getName().toUpperCase())
    .collect(Collectors.toList());

Both accomplish the same thing. LINQ integrates more deeply with C#, including query syntax that resembles SQL. Java’s Streams are purely method-based but equally capable for most tasks.

Ecosystem and Frameworks

Java’s ecosystem is massive and mature. Major frameworks include:

  • Spring / Spring Boot – dominant for enterprise web applications
  • Jakarta EE (formerly Java EE) – enterprise standards
  • Hibernate – object-relational mapping
  • Apache Kafka – event streaming
  • Android SDK – mobile development

C#’s ecosystem centers on Microsoft technologies:

  • ASP.NET Core – web applications and APIs
  • Entity Framework – object-relational mapping
  • WPF / Windows Forms – Windows desktop applications
  • Xamarin / .NET MAUI – cross-platform mobile
  • Unity – game development

Java has broader adoption in large enterprises, especially financial services, government, and organizations with legacy systems. C# dominates in Microsoft-centric shops and game development (thanks to Unity).

IDE and Tooling

Java developers typically use IntelliJ IDEA, Eclipse, or VS Code. All are cross-platform with strong Java support.

C# developers primarily use Visual Studio (Windows, macOS) or VS Code. Visual Studio is arguably the most polished IDE available for any language, with exceptional debugging, profiling, and refactoring tools. JetBrains Rider offers a cross-platform alternative that many developers prefer.

Both ecosystems have excellent tooling. The difference is less pronounced than it was a decade ago.

Performance

Both languages compile to intermediate bytecode and use just-in-time (JIT) compilation. Performance is comparable for most applications.

C# has an edge in startup time with ahead-of-time (AOT) compilation via Native AOT in .NET 7+. Java’s GraalVM offers similar capabilities but isn’t as integrated into the standard toolchain.

For raw computational performance, benchmarks show mixed results depending on the workload. Neither language is significantly faster than the other for typical business applications. Both are slower than C++ or Rust for performance-critical systems programming.

Job Market

Java job postings outnumber C# globally. Java’s head start and enterprise adoption created a larger installed base. Financial services, healthcare, government, and large corporations often standardize on Java.

C# jobs concentrate in Microsoft-ecosystem companies, game development studios (Unity), and organizations using Azure. The Windows desktop application market, while shrinking, remains solidly C#.

Salaries are comparable. Both languages are enterprise mainstays with strong demand. Geographic variation matters more than language choice – some regions lean heavily toward one or the other.

Which Should You Learn?

If you’re targeting Android development, learn Java (or Kotlin). The Android SDK is built on Java, and most Android resources assume Java knowledge.

If you want to build games with Unity, learn C#. Unity uses C# as its scripting language, and game development tutorials assume you know it.

If you’re entering enterprise development, check job postings in your area. Some markets favor Java; others favor C#. Learning either makes picking up the other straightforward.

If you’re at a Microsoft shop using Azure, Windows servers, and SQL Server, C# is the natural choice. Everything integrates smoothly.

If you’re already learning Java, continue. The language is excellent, the job market is strong, and the skills transfer to C# easily. The reverse is equally true.

Moving Forward

Java and C# will both remain relevant for decades. They target similar use cases, evolve in similar directions, and borrow features from each other. Microsoft watches Java; Oracle watches C#.

The choice between them is less about language quality and more about ecosystem fit. Where do you want to work? What do you want to build? Those answers point toward the right language.

If you’re here learning Java, you’ve made a solid choice. The fundamentals you learn – OOP, static typing, garbage collection, enterprise patterns – transfer directly to C# whenever you need them.

Related: Java vs Python | Java vs JavaScript

Sources

  • Oracle. “The Java Tutorials.” docs.oracle.com
  • Microsoft. “C# Documentation.” docs.microsoft.com
  • JetBrains. “The State of Developer Ecosystem 2023.” jetbrains.com

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