Browse questions answered by Jon Skeet

Inconsistent Timezones with GMT set in parsing LDAP date and Timestamps

I'm parsing the times from AD. There are two formats, i.e., YMD LDAP timestamps for whenCreated, whenChanged, 18-digit LDAP/FILETIME timestamps for lastLogonTimestamp, pwdLastSet,...

In the second case, you're constructing a Date and then telling it to format that date in UTC - whereas in the first case, you're parsing it in UTC, but formatting it in local time. You're already assuming that the timestamp is stored as a... more 6/8/2016 1:17:54 PM

Instantiate public object inside method

I'm trying to instantiate an object inside a method of a class so it can be used anywhere in the class. I come from a python background and it is quite easy, you can just pass...

You can't declare a field inside a method. In Java, a type either has a field, or it doesn't. Every instance of the same class has the same set of fields. But you can declare the field (not in a method) and decide to only assign a value... more 6/8/2016 6:19:29 AM

Why is add at specific index slower in LinkedLists than in ArrayLists

I was checking this chart containing performances comparisons among lists: And I find it very odd that adding and removing elements at a specific index performs faster in an...

The whole idea of a LinkedList is to improve such operations, while paying with reduced iteration performance. No, the idea of a linked list is to make adding or removing at the end or beginning very cheap... or if you have a... more 6/7/2016 4:30:00 PM

Java Can't write object as file to directory

I have a weird problem with my program. I wrote a small program to write an object to a file in a specific directory. Player-Class: package readwrite; import...

Look at this code: if (file.exists()) { file.delete(); file.createNewFile(); } else { file.mkdirs(); file.createNewFile(); } You're saying that if players/Player.ser doesn't exist, you should create it as a directory -... more 6/7/2016 3:54:19 PM

Why do wait and notify function not working properly on same class lock

Why do wait and notify function not working properly on same class lock? Please see check below code for wait and notify functionality and its output. Output:...

You're using this from an anonymous inner class - so it refers to the instance of that anonymous inner class. There are two different instances (of different anonymous inner classes) so you're calling wait() on a different object from the... more 6/7/2016 7:32:16 AM

Variant Generic Interfaces

I have a generic interface, and a class implementing that interface with a concrete type parameter. I also have a generic class using the generic interface as its type constraint,...

No - the whole point of the restriction on covariance is that it guarantees safety. A PersonRepository isn't an IRepository<DomainBase> because you can't ask it to persist any arbitrary DomainBase object. What would you expect this... more 6/6/2016 8:08:30 PM

Task.WhenAll With Different Types

I am getting a compiler error for the following line of code: IEnumerable<IPurchasedItem<IFruit>>[] result = await Task.WhenAll( ...

Task<T> is a class, and therefore invariant. So a Task<string> is not a Task<object> - and as a more complicated example, a Task<IEnumerable<IPurchasedItem<Apple>>> is not a... more 6/6/2016 7:59:21 PM

java.lang.ClassCastException at runtime or compile time

I've just read in an OCA-Book (Oracle Certified Associate), that: "Some casts exceptions can be detected as errors at compile-time, but others can only be detected at...

Or does the compiler knows only the type of the reference, not of the object (in the memory) itselfs? It only knows the type of the expression that you're trying to cast. That expression is of type Object, so it's fine to cast it to C... more 6/6/2016 11:47:04 AM

To which current class object, 'this' keyword refers too?

public class Foo { private String name; // ... public void setName(String name) { // This makes it clear that you are assigning // the value of the...

It's "whatever object the method was called on". We can't tell where the object is created, because that's presumably in some other code. Have a look at this simple, complete example: class Person { private final String name; ... more 6/6/2016 6:19:31 AM

Constructing generic types without the class/struct constraint

I've got separate implementations of a generic interface (one for classes, one for structs) and I wish to use a static Create method which handles construction. But I can't figure...

I don't think you're going to be able to do this directly, but you could easily use reflection to create the instance: Type openType = TIsAReferenceType ? typeof(SomethingForReferenceTypes<>) :... more 6/5/2016 5:00:07 PM