Windows Phone 8 - C# vs. Java

it is now time to take a look at the programming language: C# or "C sharp". I want to focus purely on the language itself and compare it to the language I know best: Java. I was surprised how good C# was compared to Java. The syntax of both languages look a lot alike. I want to highlight some of the language features I discovered while writing my first app of which I thought: wow, I wish Java would have this!

Getters and setters

Getters and setters appear to be part of the language.

1	class Person {

2	public int Age { get; set; }

3

}

Do you want the getter to be public and the setter only accessible from within the class (private)? No problem!

1	class Person {

2	public int Age { get; private set; }

3

}

As you can see, this is way shorter than implementing a default getter and/or setter in Java. Note that in C#, public properties and methods start with a capital letter. This is unlike Java, where those types of symbols start with a lower case letter.
If you decide to have custom logic (which is hardly ever the case) in your getter or setter you can still do so.

1	class Person {

2	private int age;

3	public int Age {

4

get {

5	return age;

6

}

7

set {

8	if (value == null) {

9	throw new ArgumentNullException("value");

10

}

11	age = value;

12

}

13

}

14

}

Calling constructors of the super class

When you create a subclass you often want it to have constructors that call the constructor of the superclass. In Java, there is a foggy compiler-rule that says you can only call the super-constructor in the first line of code in the constructor of your subclass.

1

// Java

2	public Person(String name, int age) {

3	super(name);

4	this.age = age;

5

}

If it is mandatory to do it in the first line, why not make calling the super constructor part of the language?

1

// C#

2	public Person(string name, int age) : base(name) {

3	this.age = age;

4

}

I like this way of calling the super (base) constructor a lot better. The same applies for when you want to call another constructor in the same class.

1	public Person(string name) {

2	this.name = name;

3

}

4	public Person(string name, int age) : this(name) {

5	this.age = age;

6

}

Constants

If you want to define a constant variable you want it to be static, and you want it to be immutable. In Java you have to literally write those two things down as "static" and "final".

1

// Java

2	public static final String NAME_PARAMETER = "name";

In C# you have a keyword for constant variables.

1

// C#

2	public const string NameParameter = "name";

It does the same thing but is more declarative and shorter. It isn't a big language feature but hey, every little helps!

Packages

This is more like a different keyword than a new language feature. I want to highlight it because I like the syntax better in C#. If you write a class definition, you do it using curly brackets around the definition. Why doesn't it work the same for package?

1

// Java

2	package trifork.example;

3	public class Person {

4

}

Why is package a statement of its own? Use curly brackets! And is "package" the right word for what it is? Sure, it IS a package, but what does it do? That's right, it provides a namespace for your classes. So why not call it like what it is as C# does?

1	namespace Trifork.Example {

2	public class Person {

3

}

4

}

Using another class

In Java you would write it down like this:

1

// Java

2	import trifork.example.Person;

Again this is just a keyword-thing but still, it describes what it does way better in C#.

1

// C#

2	using Trifork.Example.Person;

"Importing" a class is what we did using C, where the compiler would literally import (copy) the contents of the header-file of one class into the header file of another class. In both Java and C# this is no longer the case. So why does Java still call it "import"? Because it is familiar to C-programmers? Isn't using a better keyword for it?

String and Object are part of the language

In Java the String and Object types feel a bit like an after thought. It feels like something they added to the SDK later on when the language itself was already finished. In C# those two types are integrated into the language and therefore are keywords instead of classes.

1	string name = "My name";

2	object person = new Person(name);

Equality

Why do we have to use equals() when comparing two Java objects? Because if we would use the == operator, it would only resolve as true when both references are referring the exact same instance. Say we're comparing object1 and object2:

1

// Java

2	if (object1.equals(object2)) {

3	// Do your thing

4

}

What if both object1 and object2 can be null at some point, you even risk the program throwing a NullPointerException so you would have to write it down like this:

1

// Java

2	if (object1 == null ? object2 == null : object1.equals(object2)) {

3	// Do your thing

4

}

In C# another thing that is part of the language is object equality. You can safely use the == operator on objects, because at runtime, the Equals() method will be called. (only when object1 is not null of course)

1	if (object1 == object2) {

2	// Do your thing

3

}

One side note: in C# it is possible override the behaviour of the == operator so the behaviour could change in theory.

Better date/time API

We all know the date/time API in Java sucks, that's why many of us are using Joda Time instead. But without Joda Time you would have to write this kind of code in Java:

1

// Java

2	Date date = new Date();

3	Calendar calendar = Calendar.getInstance();

4	calendar.setTime(date);

5	calendar.add(Calendar.HOUR, 2);

6	date = calendar.getTime();

Besides the fact that this is a lot of code for something simple, it is weird that an object called "Date" also contains the time. In C# the standard date/time API already works kind of like Joda Time does.

1

// C#

2	DateTime dateTime = DateTime.Now;

3	dateTime = dateTime.AddHours(2);

Formatting dates as a string

In Java:

1	Date date = new Date();

2	DateFormat formatter = new SimpleDateFormat("dd-MM-yyyy");

3	String dateString = formatter.format(date);

C#:

1	DateTime date = DateTime.Now;

2	string dateString = date.ToString("dd-MM-yyyy");

Do I even need to explain this one?

Casting a class

Casting a class to another class can be done the same way in Java as in C#. Sometimes you want to do in-line casting to a class to be able to call one single method on it.

1	// Java & C#

2	((Duck)animal).quack();

In C# an alternative way exists to cast a class, with the "as" keyword, which makes in-line casting a class a little more readable.

1

// C#

2	(animal as Duck).quack();

Threading

Threading is also something that is part of the C# language, using the "await" and "async" keywords.

1	async Task<int> AccessTheWebAsync() {

2	HttpClient client = new HttpClient();

3	Task<string> getStringTask = client.GetStringAsync("http://msdn.microsoft.com");

4

5	// You can do work here that doesn't rely on the string from GetStringAsync.

6	DoIndependentWork();

7

8	string urlContents = await getStringTask;

9	return urlContents.Length;

10

}

If you define a method as being "async", the method will automatically be executed in the background and will return a "Task" instance immediately, which is similar to a "Future" object in Java. The calling code can "await" the result and do some independent work first.

Readonly fields

C# uses the "readonly" keyword instead of "final" in Java. Not a new feature, but again a better word for what it does.

1

// Java

2	final String name = "My name";

1

// C#

2	readonly string name = "My name";

"??" notation

Have you ever run into a situation that requires your code to return something, only if a certain variable is not null, and null if it is? You would write code like this:

1

// Java

2	public String nameForPerson(Person person) {

3	return person == null ? null : person.getName();

4

}

In C# a shorthand notation exists for this type of situation:

1

// C#

2	public string nameForPerson(Person person) {

3	return person ?? person.Name;

4

}

This shorthand notation can also be useful if you're using a singleton-like pattern:

1

// C#

2	private PersonRepository personRepository;

3

4	public PersonRepository PersonRepository() {

5	return personRepository ?? (personRepository = new PersonRepository());

6

}

Literal notation for maps and arrays

Even the inferior Objective C language has a literal notation for arrays (lists) and dictionaries (maps), so why doesn't Java have it??

1	Map<String, String> entries = new HashMap<>();

2	entries.put("a", "apple");

3	entries.put("b", "banana");

4

5	String apple = entries.get("a");

Anyway, C# has a literal notation for this:

1	var entries = new Dictionary<string, string> {

2	{ "a", "apple" },

3	{ "b", "banana" }

4

};

5	string apple = entries["a"];

A similar thing works for lists:

1	var list = new List<string> { "apple", "banana" };

2	string apple = list[0];

SQL is part of the language

Search through lists like this:

1	var results = from p in list

2	where p.Age > 18

3

select p;

This will give you all Person objects in the "list" where the age is more than 18. You can also do similar things using LINQ and lambda expressions:

1	var results = list.Where(person => person.Age > 18);

Instead of searching for specific people, you want a list of all names of those people? No problem!

1	var names = list.Select(person => perons.Name);

Using pointers

Many people get goose bumps when they hear the word "pointer" because they know what a mess you can make of your code when you have to use pointers directly. In C# you of course mainly use references, just like in Java. But sometimes pointers can be very handy. What if you create a method and you would like to return multiple values? In Java I always create a new class containing each value as a field, and instantiate that class and use it to return mulitple values. In C# you can simply use the "out" keyword that works like a pointer.

1	class OutReturnExample {

2	public void OutMethod(out int value, out string text) {

3	value = 44;

4	text = "I've been returned";

5

}

6	public void DoIt() {

7	int value;

8	string text;

9	OutMethod(out value, out text);

10	// value is now 44

11	// text is now "I've been returned"

12

}

13

}

Overriding methods

And finally, not a new feature, but again something that is part of the language where in Java it isn't, which makes it nicer.

1

// Java

2

@Override

3	public String toString() {

4	return "description";

5

}

1

// C#

2	public override string ToString() {

3	return "description";

4

}

Probably many more features

C# probably has many more features I did not discover in the short time I have worked with it so far but I am eager to discover them!

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