c# and java diffs

**=?ISO-8859-1?Q?Arne_Vajh=F8j?=** · Jun 27 '08, 07:51 PM

Re: c# and java diffs

Daniel wrote:

Hi all,
>
I have some questions regarding C#. I come from a Java background. I am
using .NET 1.1. Please limit your answers to v 1.1, otherwise please
state the version to which it applies to.
>
1) I have seen code like this:
>
public void someMethod() {
// code
MyObject otherVar;
using (SomeClass var = DifferentClass. method()) {
otherVar = someOtherObject .method();
}
}
>
What is happening here? What is the part that begins with "using"? And
what is the purpose of putting that whole thing inside the "using"? Why
not just:
>
MyObject otherVar = someOtherObject .method();

It means:

public void someMethod() {
// code
MyObject otherVar;
SomeClass var;
try
{
var = DifferentClass. method())
otherVar = someOtherObject .method();
}
finally
{
if(var != null)
{
var.Dispose(); // usually equivalent to var.Close()
}
}
}

2) What are delegates, how are they used, and why would you use them?
Can you provide a simple example?

Delegate are method pointers.

Java often uses anonymous classes to achieve the same.

Example snippet (you should be able to figure it out):

public delegate void Processor(strin g s);
public static void Permute(List<Li st<String>data, Processor
p)
{
...
p(prefix + s);
...
}
public static void Print(string s)
{
Console.WriteLi ne(s);
}
public static void Main(string[] args)
{
...
Permute(data, Print);
}

3) Are there inner classes? In Java, it's a class defined within another
class, which may or may not be accessible outside of the class.
>
For example:
>
public class A {
public static class B {
public void methodInB() { ... }
}
}
>
B can be instantiated by : A.B b = new A.B();

Yes.

4) Are there anonymous inner classes?
>
For example:
>
public class A {
public void methodInA() {
var.addActionLi stener() { new ActionListener( ) {
public void actionPerformed (Object a) {
}
}
}
}
>
The inner anonymous class is the new ActionListener( ).

No. You would use delegates and in higher versions anonymous
methods or lambda expressions.

5) Is there a "javadoc" like thing for methods in C#?
I see stuff like:
>
/// <summary>
/// text...
/// </summary>
/// <param name...
>
I am guessing that is the C# javadoc equivalent. If so, how are the docs
generated, and does it create an HTML output?

Download Visual Studio 2003 Retired Technical documentation from Official Microsoft Download Center

http://msdn.microsoft.com/en-us/library/b2s063f7(VS.71).aspx

The content you requested has already been retired. It is available to download on this page.

6) VS.NET 2003 question
Is there a way to point at a class or variable and ask the IDE all the
places that it's being used in? For example, if I have class A, then
give me all the places class A is being used (for example of all the
class A instantions or all the places static methods of class A are
being used). Same with variables, if I have an instance variable in
class A, show me everywhere this var is being used.

No idea.

7) Does 1.1 provide generics? Even if it does not, can you please
provide a simple example?
>
The java equivalent would be:
List<Stringlist String = new ArrayList<Strin g>();
listString.add( "my string...");
listString.add( "2nd string...");
// to iterate
for(String s : listString) {
System.out.prin tln(s);
}
>
I'd like to see some of the generic creation syntax of C#.

No. That requires .NET 2.0+ and VS 2005+.

8) Is version .NET 2 backwards compatible with 1.1? Can I use VS C#
Express 2005 on a VS.NET 2003 project? Can I specify in 2005 Express
that I want to compile for .NET 1.1?

No.

But in 2008 you can choose between 3.5 and 2.0.

Arne

**Peter Duniho** · Jun 27 '08, 07:51 PM

Re: c# and java diffs

On Wed, 14 May 2008 18:11:15 -0700, Daniel <dhw4095@gmail. com.nospam
wrote:

Hi all,
>
I have some questions regarding C#. I come from a Java background. I am
using .NET 1.1. Please limit your answers to v 1.1, otherwise please
state the version to which it applies to.

Here is a web site you may find useful:

http://msdn.microsoft.com/en-us/library/default.aspx

1) I have seen code like this:
>
public void someMethod() {
// code
MyObject otherVar;
using (SomeClass var = DifferentClass. method()) {
otherVar = someOtherObject .method();
}
}
>
What is happening here? What is the part that begins with "using"?

See:

using statement - ensure the correct use of disposable objects - C# reference

http://msdn.microsoft.com/en-us/library/yh598w02.aspx

Use the C# using statement or declaration to ensure the correct use of disposable objects

[...]
2) What are delegates, how are they used, and why would you use them?
Can you provide a simple example?

See:

Built-in reference types - C# reference

http://msdn.microsoft.com/en-us/library/900fyy8e.aspx

Learn about reference types that have C# keywords you can use to declare them.

Work with delegate types in C# - C#

http://msdn.microsoft.com/en-us/library/ms173171.aspx

Explore delegate types in C#. A delegate is a date type that refers to a method with a defined parameter list and return type. You use delegates to pass methods as arguments to other methods.

3) Are there inner classes? In Java, it's a class defined within another
class, which may or may not be accessible outside of the class.

See:

Nested Types - C#

http://msdn.microsoft.com/en-us/library/ms173120.aspx

A type defined within a class, struct, or interface is called a nested type in C#.

The short answer is "no". C# has nested classes (equivalent to Java
"static nested classes"), but not inner classes. Of course, you can
always pass a reference to the outer class when constructing the nested
class to accomplish the same thing explicitly. As in Java, C# nested
classes have access to private members of the outer class.

[...]
4) Are there anonymous inner classes?

Sort of.

C# 3.0 introduced anonymous classes, if I understand the "var" type
correctly. However, as far as I know, this doesn't provide the full
degree of functionality that Java's anonymous classes would. In
particular, an anonymous type can contain only properties, and not
methods, events, etc.

However, note that in Java one of the most common reasons for using an
anonymous class is addressed in .NET/C# using delegates and events instead.

See:

Anonymous types - C#

http://msdn.microsoft.com/en-us/library/bb397696.aspx

Learn about C# anonymous types, which provide a way to create objects with read-only properties without defining a named type first.

Implicitly typed local variables - C#

http://msdn.microsoft.com/en-us/library/bb384061.aspx

The var keyword in C# instructs the compiler to infer the type of the variable from the expression on the right side of the initialization statement.

Declaration statements - local variables and constants, var, local reference variables (ref locals) - C# reference

http://msdn.microsoft.com/en-us/library/bb383973.aspx

Declaration statements introduce a new local variable, local constant, or local reference variable (ref local). Local variables can be explicitly or implicitly typed. A declaration statement can also include initialization of a variable's value.

[...]
5) Is there a "javadoc" like thing for methods in C#?
I see stuff like:
>
/// <summary>
/// text...
/// </summary>
/// <param name...
>
I am guessing that is the C# javadoc equivalent. If so, how are the docs
generated, and does it create an HTML output?

Those are XML comments, and the compiler uses them to generate a separate
XML document that goes with the output. The IDE then can use that for
context-sensitive help. I don't know if it can be used to generate HTML
output.

See:

http://msdn.microsoft.com/en-us/library/b2s063f7.aspx

6) VS.NET 2003 question
Is there a way to point at a class or variable and ask the IDE all the
places that it's being used in?

I'm not sure. For sure, 2005 and 2008 versions support this.

You should really consider upgrading to 2008. Even if you can only use
the free Express version, that's likely to be a significant improvement
over being stuck with 2003 and especially .NET 1.1

[...]
7) Does 1.1 provide generics? Even if it does not, can you please
provide a simple example?

No. Generics were introduced in C# 2.0. I assume by "simple example" you
mean a C# 2.0 example, not a 1.0 (.NET 1.1) example.

The java equivalent would be:
List<Stringlist String = new ArrayList<Strin g>();
listString.add( "my string...");
listString.add( "2nd string...");
// to iterate
for(String s : listString) {
System.out.prin tln(s);
}
>
I'd like to see some of the generic creation syntax of C#.

Well, your example is using generics, not defining one. And I don't think
it's correct, as the type is ArrayList, not List as you've declared the
variable.

Anyway, the equivalent is practically the same:

List<Stringlist String = new List<String>();

listString.Add( "my string...");
listString.Add( "2nd string...");

foreach (String s in listString)
{
Console.WriteLi ne(s);
}

8) Is version .NET 2 backwards compatible with 1.1?

Mostly, yes. You may want to read MSDN's documentation on specific
changes. In a very few places, new versions of .NET significantly change
behavior. This happened much more with the 1.1 to 2.0 transition than
with later ones. Things like how unhandled exceptions are dealt with,
thread pool size, and some other were changed.

Can I use VS C# Express 2005 on a VS.NET 2003 project?

You can import it, yes. But it won't be a 2003 project any longer.

Can I specify in 2005 Express that I want to compile for .NET 1.1?

No. 2008 provides for specifying a specific target version of .NET, but
only down to 2.0.

Pete

**Peter Duniho** · Jun 27 '08, 07:51 PM

Re: c# and java diffs

On Wed, 14 May 2008 18:29:22 -0700, Arne VajhÃ¸j <arne@vajhoej.d kwrote:

[...]

> What is happening here? What is the part that begins with "using"? And
>what is the purpose of putting that whole thing inside the "using"? Why
>not just:
> MyObject otherVar = someOtherObject .method();

>
It means:
>
public void someMethod() {
// code
MyObject otherVar;
SomeClass var;
try
{
var = DifferentClass. method())
otherVar = someOtherObject .method();
}
finally
{
if(var != null)
{
var.Dispose(); // usually equivalent to var.Close()
}
}
}

Almost. The variable used in the "finally" clause is actually a hidden,
private variable known only to the compiler. Changes to the variable
"var" will not affect the disposal when using a "using" statement, while
it would in the above code. Also, the initialization of the "var"
variable is outside the try/finally block, not inside.

It also implies a cast to IDisposable before calling Dispose() (since not
all classes implement IDisposable implicitly).

And one final note: it's true that many classes that define both Close()
and Dispose() will make both functionally equivalent to each other.
However, this is far from guaranteed, and many classes implementing
IDisposable don't have a Close() method at all.

[...]
But in 2008 you can choose between 3.5 and 2.0.

And .NET 3.0 as well, in case that wasn't clear.

Pete

**Tim Jarvis** · Jun 27 '08, 07:51 PM

Re: c# and java diffs

Arne Vajhøj wrote:

6) VS.NET 2003 question
Is there a way to point at a class or variable and ask the IDE all
the places that it's being used in? For example, if I have class
A, then give me all the places class A is being used (for example
of all the class A instantions or all the places static methods of
class A are being used). Same with variables, if I have an
instance variable in class A, show me everywhere this var is being
used.

>
No idea.

I don't think so in VS2003 (I'm using 2008 so can't check), however you
can get this functionality from Lutz Roeders excellent tool "Reflector"
using the Analyze function if you don't already have reflector, you
really should go get it (http://www.aisto.com/roeder/dotnet/), it's a
must have tool for any .NET developer.

Regards Tim.

**Chris Shepherd** · Jun 27 '08, 07:51 PM

Re: c# and java diffs

Peter Duniho wrote:

>I am guessing that is the C# javadoc equivalent. If so, how are the
>docs generated, and does it create an HTML output?

>
Those are XML comments, and the compiler uses them to generate a
separate XML document that goes with the output. The IDE then can use
that for context-sensitive help. I don't know if it can be used to
generate HTML output.

Sandcastle (http://www.codeplex.com/Sandcastle) has a "website" build mode which
generates HTML.

Chris.

c# and java diffs

c# and java diffs

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