constructor - w3toppers.com

Difference between a no-arg constructor and a default constructor in Java

The default constructor is a no-args constructor that the Java compiler inserts on your behalf; it contains a default call to super(); (not supper()) which is the default behavior. If you implement any constructor then you no longer receive a default constructor. JLS-8.8.9. Default Constructor says (in part), If a class contains no constructor declarations, … Read more

Create new object using reflection?

You need to locate the exact constructor for this. Class.newInstance() can only be used to call the nullary constructor. So write final Value v = Value.class.getConstructor( int.class, int.class, double.class).newInstance(_xval1,_xval2,_pval);

Delphi: Understanding constructors

I see two reasons your original set of declarations shouldn’t compile cleanly: There should be a warning in TCellPhone that its constructor hides the method of the base class. This is because the base-class method is virtual, and the compiler worries that you’re introducing a new method with the same name without overriding the base-class … Read more

Why can’t I refer to an instance method while explicitly invoking a constructor?

Non-static methods are instance methods. This are only accessible in existing instance, and instance does not exist yet when you are in constructor (it is still under construction). Why it is so? Because instance methods can access instance (non-static) fields, which can have different values in different instances, so it doesn’t make sense to call … Read more

Closing a form during a constructor

Calling Close from the constructor of the Form is not possible, as it will call Dispose on a Form that has not yet been created. To close the Form after construction, assign an anonymous event handler to the Load event that closes your Form before it is displayed for the first time: public partial class … Read more

a constructor as a delegate – is it possible in C#?

I’m assuming you would normally do something like this as part of a factory implementation, where the actual types aren’t known at compile-time… First, note that an easier approach may be a post-create init step, then you can use generics: static T Create<T>({args}) where T : class, ISomeInitInterface, new() { T t = new T(); … Read more

C++ Constructor/Destructor inheritance

Terminology, terminology… OK, what do we mean by “Foo is inherited”? We mean that if objects of class A have Foo in its interface, then objects of class B which is a subclass of A also have Foo in its interface. Constructors aren’t a part of objects’ interface. They belong directly to classes. Classes A … Read more

Cannot reference “X” before supertype constructor has been called, where x is a final variable

The reason why the code would not initially compile is because defaultValue is an instance variable of the class Test, meaning that when an object of type Test is created, a unique instance of defaultValue is also created and attached to that particular object. Because of this, it is not possible to reference defaultValue in … Read more

Calling a constructor to re-initialize object

Sort of. Given a class A: A a; … a = A(); the last statement is not initialisation, it is assignment, but it probably does what you want.