Java vs C#: Key Syntax Differences

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Java and C# are both object-oriented programming languages with similar syntax, but they have distinct differences that can be confusing, especially for developers who switch between them frequently. This document highlights the key syntax differences between Java and C# to help junior developers avoid common pitfalls and write more efficient code.

1. Basic Syntax and Data Types

Variable Declaration

Java:

int number = 10;
String text = "Hello";

C#:

int number = 10;
string text = "Hello";

Key Difference: In C#, primitive types (e.g., int, double, char) and their corresponding object types (e.g., String) follow Pascal case (String vs string). Java uses String with an uppercase ‘S’ consistently.

Type Inference

C# supports type inference using the var keyword:

var number = 10; // Compiler infers as int

Java supports type inference with var (Java 10+):

var number = 10; // Compiler infers as int

Key Difference: Type inference is available in both languages, but C# introduced it much earlier.

Constants

Java:

final int MAX_VALUE = 100;

C#:

const int MaxValue = 100;
readonly int ReadOnlyValue = 200;

Key Difference: Java uses final for constants, whereas C# uses const for compile-time constants and readonly for runtime-initialized values. C# also follows PascalCase for constant naming, while Java typically uses UPPER_CASE with underscores.

2. Classes and Methods

Class Declaration

Java:

public class MyClass {
    private int value;
    
    public MyClass(int value) {
        this.value = value;
    }
}

C#:

public class MyClass {
    private int value;
    
    public MyClass(int value) {
        this.value = value;
    }
}

Properties (C# Only)

public class Person {
    public string Name { get; set; }
}

Java requires explicit getter and setter methods:

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

Key Difference: C# provides a more concise way to define properties using get and set, reducing boilerplate code.

3. Memory Management and Garbage Collection

Both Java and C# use garbage collection for automatic memory management. However, C# also provides manual memory management capabilities through the IDisposable interface and the using statement.

C#:

public class MyResource : IDisposable {
    public void Dispose() {
        // Cleanup resources
    }
}

using (var resource = new MyResource()) {
    // Use resource
}

Java:

try (BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
    // Use resource
}

4. Structs vs Classes

C# supports struct, which is a lightweight alternative to a class.

public struct Point {
    public int X { get; set; }
    public int Y { get; set; }
}

Java does not support structs:

// Not available in Java

Key Difference: C# allows the use of value-type structs, while Java only has reference types.

5. Exception Handling

Java requires checked exceptions, while C# does not.

Java:

public void readFile() throws IOException {
    throw new IOException("File not found");
}

C#:

public void ReadFile() {
    throw new IOException("File not found");
}

6. Multithreading and Asynchronous Programming

C# supports async and await, making asynchronous programming simpler than Java’s Future and ExecutorService.

C#:

public async Task<string> GetDataAsync() {
    return await Task.FromResult("Hello");
}

Java:

ExecutorService executor = Executors.newSingleThreadExecutor();
Future<String> future = executor.submit(() -> "Hello");
String result = future.get();

7. LINQ vs Streams

C# uses LINQ (Language-Integrated Query), while Java uses Streams for functional-style operations on collections.

C#:

var numbers = new List<int> {1, 2, 3, 4, 5};
var evenNumbers = numbers.Where(n => n % 2 == 0).ToList();

Java:

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
List<Integer> evenNumbers = numbers.stream()
                                   .filter(n -> n % 2 == 0)
                                   .collect(Collectors.toList());

8. Operator Overloading

C# supports operator overloading, while Java does not.

C#:

public class Complex {
    public int Real { get; set; }
    public int Imaginary { get; set; }
    
    public static Complex operator +(Complex a, Complex b) {
        return new Complex { Real = a.Real + b.Real, Imaginary = a.Imaginary + b.Imaginary };
    }
}

Java does not allow operator overloading:

// Not possible in Java

9. Indexers (C# Only)

C# allows defining indexers in a class:

public class SampleCollection {
    private int[] array = new int[100];
    public int this[int i] {
        get { return array[i]; }
        set { array[i] = value; }
    }
}

Java does not support indexers explicitly.

Key Difference: C# allows defining indexers to access elements using array-like syntax.

Conclusion

While Java and C# share many similarities, key differences exist in properties, memory management, exception handling, asynchronous programming, and additional features like LINQ, indexers, structs, and operator overloading. Understanding these differences helps developers write cleaner, more efficient code when switching between the two languages.

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