static interview questions
Top static frequently asked interview questions
I'm a fan of extension methods in C#, but haven't had any success adding an extension method to a static class, such as Console.
For example, if I want to add an extension to Console, called 'WriteBlueLine', so that I can go:
Console.WriteBlueLine("This text is blue");
I tried this by adding a local, public static method, with Console as a 'this' parameter... but no dice!
public static class Helpers {
public static void WriteBlueLine(this Console c, string text)
{
Console.ForegroundColor = ConsoleColor.Blue;
Console.WriteLine(text);
Console.ResetColor();
}
}
This didn't add a 'WriteBlueLine' method to Console... am I doing it wrong? Or asking for the impossible?
Source: (StackOverflow)
I'd like to have a private static constant for a class (in this case a shape-factory).
I'd like to have something of the sort.
class A {
private:
static const string RECTANGLE = "rectangle";
}
Unfortunately I get all sorts of error from the C++ (g++) compiler, such as:
ISO C++ forbids initialization of
member ‘RECTANGLE’
invalid in-class initialization of static data member of non-integral type ‘std::string’
error: making ‘RECTANGLE’ static
This tells me that this sort of member design is not compliant with the standard. How do you have a private literal constant (or perhaps public) without having to use a #define directive (I want to avoid the uglyness of data globality!)
Any help is appreciated. Thanks.
Source: (StackOverflow)
I have several classes that do not really need any state. From the organizational point of view, I would like to put them into hierarchy.
But it seems I can't declare inheritance for static classes.
Something like that:
public static class Base
{
}
public static class Inherited : Base
{
}
will not work.
Why have the designers of the language closed that possibility?
Source: (StackOverflow)
I have a class with a private static final field that, unfortunately, I need to change at run-time.
Using reflection I get this error: java.lang.IllegalAccessException: Can not set static final boolean field
Is there any way to change the value?
Field hack = WarpTransform2D.class.getDeclaredField("USE_HACK");
hack.setAccessible(true);
hack.set(null, true);
Source: (StackOverflow)
How can one get the name of the class from a static method in that class. For example
public class MyClass {
public static String getClassName() {
String name = ????; // what goes here so the string "MyClass" is returned
return name;
}
}
To put it in context, I actually want to return the class name as part of a message in an exception.
Source: (StackOverflow)
How do you create a static class in C++? I should be able to do something like:
cout << "bit 5 is " << BitParser::getBitAt(buffer, 5) << endl;
Assuming I created the BitParser class. What would the BitParser class definition look like?
Source: (StackOverflow)
public class EnumRouteConstraint<T> : IRouteConstraint
where T : struct
{
private static readonly Lazy<HashSet<string>> _enumNames; // <--
static EnumRouteConstraint()
{
if (!typeof(T).IsEnum)
{
throw new ArgumentException(Resources.Error.EnumRouteConstraint.FormatWith(typeof(T).FullName));
}
string[] names = Enum.GetNames(typeof(T));
_enumNames = new Lazy<HashSet<string>>(() => new HashSet<string>
(
names.Select(name => name), StringComparer.InvariantCultureIgnoreCase
));
}
public bool Match(HttpContextBase httpContext, Route route, string parameterName, RouteValueDictionary values, RouteDirection routeDirection)
{
bool match = _enumNames.Value.Contains(values[parameterName].ToString());
return match;
}
}
Is this wrong? I would assume that this actually has a static readonly field for each of the possible EnumRouteConstraint<T> that I happen to instance.
Source: (StackOverflow)
In Java, what's the difference between:
private final static int NUMBER = 10;
and
private final int NUMBER = 10;
Both are private and final, the difference is the static attribute.
What's better? And why?
Source: (StackOverflow)
I have a few static pages that are just pure HTML, that we display when the server goes down. How can I put a favicon that I made (it's 16x16px and it's sitting in the same directory as the HTML file; it's called favicon.ico) as the "tab" icon as it were. I followed the rules I have read up on and no dice. I read a post that suggested the following as a link in the head section of the pages.
<link rel="icon" rel='nofollow' href="favicon.ico" type="image/x-icon"/>
<link rel="shortcut icon" rel='nofollow' href="favicon.ico" type="image/x-icon"/>
But it still doesn't want to work. I am using Chrome to test the sites. According to Wikipedia .ico is the best pic format that runs on all browser types.
Source: (StackOverflow)
This question already has an answer here:
I was looking over some code the other day and I came across:
static {
...
}
Coming from C++, I had no idea why that was there. Its not an error because the code compiled fine. What is this "static" block of code?
Source: (StackOverflow)
To be specific, I was trying this code:
package hello;
public class Hello {
Clock clock = new Clock();
public static void main(String args[]) {
clock.sayTime();
}
}
But it gave the error
Cannot access non-static field in static method main
So I changed the declaration of clock to this:
static Clock clock = new Clock();
And it worked. What does it mean to put that keyword before the declaration? What exactly will it do and/or restrict in terms of what can be done to that object?
Source: (StackOverflow)
This question already has an answer here:
What is the difference between static and non static inner class?
Source: (StackOverflow)
I am converting a PHP 5.3 library to work on PHP 5.2. The main thing standing in my way is the use of late static binding like return new static($options); , if I convert this to return new self($options) will I get the same results?
What is the difference between new self and new static?
Source: (StackOverflow)