C# for Java Developers

C#
for
Java
Developers

Jussi
Pohjolainen

Tampere
University
of
Applied
Sciences

Overview

•  Ecma
and
ISO
Standard

•  Developed
by
MicrosoD,
uses
in
.NET
and

WP7

•  Most
recent
version
is
C#
4.0

Common
Language
Infrastructure
(CLI)

CLI

•  CLI
is
an
open
speciﬁcaRon
that
describes

executable
code
and
runRme
environment

•  CLI
is
core
of

–  MicrosoD
.NET
Framework

–  Mono
(Open
Source)

–  Portable.net
(Open
Source)

CTS,
CLS,
VES,
CIL

•  Common
Type
System
(CTS)

–  A
set
of
data
types
and
operaRons
that
are
share
by
all

CTS-‐compliant
programming
languages,
such
as
C#
and
VB

•  Common
Language
SpeciﬁcaRon
(CLS)

–  Set
of
base
rules
to
which
any
language
targeRng
the
CLI

should
conform.

•  Virtual
ExecuRon
System
(VES)

–  VES
loads
and
executes
CLI-‐compaRble
programs

•  Common
Intermediate
Language
(CIL)

–  Intermediate
language
that
is
abstracted
from
the

plaXorm
hardware
(In
Java:
class)

.NET
on
Windows
7

Add
C:WindowsMicrosoft.NETFrameworkv3.5 to
path!

Common
Language
RunRme:
Mac

Dropbox
–

folder

Common
Language
RunRme:
Win

And
run

the
.exe
in

Windows!

Almost
the
Same
but
Not
Quite

C#

Keywords

•  Single
rooted
class
hierarchy:
all
objects

inheritate
System.Object

•  Almost
every
keyword
in
Java
can
be
found

from
C#

–  super -> base
–  instanceof -> is
–  import -> using
–  extends / implements -> :
•  Otherwise,
pre`y
much
the
same

Memory
Handling
and
RunRme

•  Memory
Handling

–  Most
objects
in
C#
to
heap
using
new

–  CLR
handles
garbage
collecRons

•  RunRme

–  C#
is
compiled
to
intermediate
langage
(IL)

–  IL
runs
on
top
of
CLR

–  IL
code
is
always
naRvely
compiled
before
running

OO

•  No
global
methods,
just
like
in
Java

•  Interface
is
pure
abstract
class

•  No
mulRple
inheritance

Main

using System;

class A {

public static void Main(String[] args){

Console.WriteLine("Hello World");

}
}

Compiling
Several
Files
in
C#

C:CodeSample> csc /main:A /out:example.exe A.cs B.cs

C:CodeSample> example.exe
Hello World from class A

C:CodeSample> csc /main:B /out:example.exe A.cs B.cs

C:CodeSample> example.exe
Hello World from class B

Inheritance:
Base
Class

using System;
abstract public class Figure {
private int x;
private int y;
public Figure(int x, int y) {
this.x = x;
this.y = y;
}
public void SetX(int x) {
this.x = x;
}
public void SetY(int y) {
this.y = y;
}
public int GetY() {
return y;
}
public int GetX() {
return x;
}
public abstract double CalculateSurfaceArea();
}

Inheritance:
Interface

interface IMove {
void MoveTo(int x, int y);
}

Inheritance

public class Rectangle : Figure, IMove {
private int width;
private int height;

public Rectangle(int x, int y, int width, int height) : base(x,y) {
this.width = width;
this.height = height;
}

public void MoveTo(int x, int y) {
SetX( GetX() + x );
SetY( GetY() + y );
}

public override double CalculateSurfaceArea() {
return width * height;
}

public static void Main(String [] args) {
Rectangle r = new Rectangle(4, 5, 10, 10);
Console.Write( "Rectangle x: " );
Console.Write( r.GetX() );
r.MoveTo(5, 0);
Console.Write( "nRectangle y: " );
Console.Write( r.GetX() );
Console.Write( "nRectangle Surface Area: " );
Console.Write( r.CalculateSurfaceArea() );
Console.Write( "n" );
}
}

Run
Time
Type
IdenRﬁcaRon

Object rectangleObject = new Rectangle(4, 5, 10, 10);

// Type cast from Object to Rectangle
Rectangle temp1 = rectangleObject as Rectangle;

// Check if cast was successfull
if(temp1 != null) {
Console.Write("Success: Object was casted to Rectangle!");
temp1.SetX(0);
}
}

ProperRes

public class Rectangle : Figure, IMove {
private int height;
private int width;

public int Width {
get {
return width;
}
set {
if(value > 0) {
width = value;
} else {
Console.WriteLine("Value was not set.");
}
}
}

public Rectangle(int x, int y, int width, int height) : base(x,y) {
this.width = width;
this.height = height;
}

…

Rectangle r = new Rectangle(5,5,10,10);
r.Width = 10;
Console.Write(r.Width);
// Value was not set
r.Width = -5;
}
}

Alias

using Terminal = System.Console;

class Test {
public static void Main(string[] args){
Terminal.WriteLine("Please don’t use this");
}
}

Namespaces

using System;

namespace fi.tamk.tiko.ohjelmistotuotanto {
public class Test {
public static void method() {
Console.Write("ohjelmistotuotanton");
}
}
}

namespace fi.tamk.tiko.pelituotanto {
public class Test {
public static void method() {
Console.Write("pelituotanton");
}
}
}

class App {
fi.tamk.tiko.ohjelmistotuotanto.Test.method();
fi.tamk.tiko.pelituotanto.Test.method();
}
}

Constant
Variables

•  const int VARIABLE = 10;

Variable
Length
Parameters
and
foreach

using System;

public class Params {

public static void Method(params int[] array) {
foreach(int num in array) {
Console.Write(num);
Console.Write("n");
}
}

Method(1,2,3,4,5);
Method(1,2);

int [] myArray = {1,2,3,4};
Method(myArray);
}
}

OperaRon
Overloading

using System;

public class MyNumber {

private int value;

public MyNumber(int value) {
this.value = value;
}

public static MyNumber operator+(MyNumber number1, MyNumber number2) {
int sum = number1.value + number2.value;
MyNumber temp = new MyNumber(sum);

return temp;
}

MyNumber number1 = new MyNumber(5);
MyNumber number2 = new MyNumber(5);

MyNumber sum = number1 + number2;

Console.Write(sum.value);
}
}

ParRal
Types

•  The
parRal
types
feature
enables
one
to

define
a
single
class
across
mul/ple
source

files!

•  So
one
class
can
be
declared
in
several
files!

C# for Java Developers

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