boxing

I found the following code snippet while searching about boxing and unboxing in C#. class TestBoxing { static void Main() { int i = 123; // Boxing copies the value of i into object o. object o = i; // Change the value of i. i = 456; // The change in i does not effect the value stored in o. System.Console.WriteLine("The value-type value = {0}", i); System.Console.WriteLine("The object-type value = {0}", o); } } /* Output: The value-type value = 456 The object-type value = 123 */ Over here it says that even though he value of i changes the value of o remains the same.If so then o is referencing

I'm taking an iterator of some type that must implement the trait A , and trying to convert it into a Vec of Box es of that trait: trait A {} fn test2<'a, I>(iterator: I) -> Vec<Box<A + 'a>> where I: IntoIterator, I::Item: A + 'a, { iterator .into_iter() .map(|a| Box::new(a)) .collect::<Vec<Box<A + 'a>>>() } However, this fails to compile, saying: error[E0277]: the trait bound `std::vec::Vec<std::boxed::Box<A + 'a>>: std::iter::FromIterator<std::boxed::Box<<I as std::iter::IntoIterator>::Item>>` is not satisfied --> src/main.rs:11:10 | 11 | .collect::<Vec<Box<A + 'a>>>() | ^^^^^^^ a collection

There's a general advice to use Integer.valueOf(int) instead of new Integer(int) because of caching. In JDK 5+, you should really use valueOf because Integer now caches Integer objects between -128 and 127 and can hand you back the same exact Integer(0) object every time instead of wasting an object construction on a brand new identical Integer object. How can extend the range? You can use the java.lang.Integer.IntegerCache.high property to increase the size of this cache. ex : java -Djava.lang.Integer.IntegerCache.high=4096 SomeClass.class My questions to you are: 1) Why is your code making

I came across an extension method that applies to structs (SomeStruct) and returns whether or not the value is equal to the default(SomeStruct) (when the parameterless constructor is called). public static bool IsDefault<T> (this T value) where T : struct { return (!EqualityComparer<T>.Default.Equals(value, default(T))); } This got me wondering whether the struct was being boxed. This is purely out of curiosity as there are pros/cons to boxing/passing by value depending on the context. Assumptions: The first of the following methods is illegal since structs do not implicitly override the

I have an interface IEntity public interface IEntity{ bool Validate(); } And I have a class Employee which implements this interface public class Employee : IEntity{ public bool Validate(){ return true; } } Now if I have the following code Employee emp1 = new Employee(); IEntity ent1 = (IEntity)emp1; // Is this a boxing conversion? If it is not a boxing conversion then how does the cast work? No, since Employee is a class, which is a reference type rather than a value type . From MSDN : Boxing is the process of converting a value type to the type object or to any interface type implemented by

I recently came across this Stackoverflow question: When to use struct? In it, it had an answer that said something a bit profound: In addition, realize that when a struct implements an interface - as Enumerator does - and is cast to that implemented type, the struct becomes a reference type and is moved to the heap. Internal to the Dictionary class, Enumerator is still a value type. However, as soon as a method calls GetEnumerator(), a reference-type IEnumerator is returned. Exactly what does this mean? If I had something like struct Foo : IFoo { public int Foobar; } class Bar { public IFoo