constructor-chaining

This question already has answers here : Closed 6 years ago . How to avoid constructor code redundancy in Java? (4 answers) Hi I am just learning about constructor chaining in Java and had some questions... First of all could someone please explain when I would ever need to use this? Off the top of my head I seriously cannot think of a situation. In this example, within the constructor with no arguments I call another constructor. How do I access this new "James Bond" object for future use? import java.util.*; class Employee { private String name; private double salary; public Employee() {

Before I started using Code Contracts I sometimes ran into fiddlyness relating to parameter validation when using constructor chaining. This is easiest to explain with a (contrived) example: class Test { public Test(int i) { if (i == 0) throw new ArgumentOutOfRangeException("i", i, "i can't be 0"); } public Test(string s): this(int.Parse(s)) { if (s == null) throw new ArgumentNullException("s"); } } I want the Test(string) constructor to chain the Test(int) constructor, and to do so I use int.Parse() . Of course, int.Parse() doesn't like having a null argument, so if s is null it will throw

Today Recently on Stackoverflow i learned that: reintroduce is used to hide ancestor constructors reintroduce is used to show ancestor constructors i've been trying to make sense of it all, so here is a another, very specific question, supporting my main question dealing with constructors . Update: replaced the entire question: TComputer = class(TObject) public constructor Create(Teapot: string=''); end; TCellPhone = class(TComputer) public constructor Create(Cup: Integer); overload; virtual; constructor Create(Cup: Integer; Teapot: string); overload; virtual; end; When constructing TCellPhone

Update: The example i originally had was kind of complex. Here's a simple 8 line example that explains everything in one code block. The following does not compile gives a warning: TComputer = class(TObject) public constructor Create(Cup: Integer); virtual; end; TCellPhone = class(TComputer) public constructor Create(Cup: Integer; Teapot: string); virtual; end; Note: This question is part 3 in my ongoing series of questions about the subtlties of constructors in Delphi Original question How can i add a constructor to an existing class? Let's give an hypothetical example (i.e. one that i'm

Every now and then, I bump into syntax that I've seen before, but never used. This is one of those times. Can someone explain the purpose of ":this" or ":base" following a C# constructor method? For example: public MyClass(SomeArg arg) : this(new SomethingElse(), arg) { } My gut feeling is that it is used to map a default argument onto another constructor method. You're basically right. this() calls a constructor on the current instance, base() calls the supertype's constructor on current instance. They're generally used to handle constructor overloads so you can add additional options without

My understanding of constructor chaining is that , when there are more than one constructors in a class (overloaded constructors) , if one of them tries to call another constructor,then this process is called CONSTRUCTOR CHAINING , which is not supported in C++ . Recently I came across this paragraph while reading online material.... It goes like this ... You may find yourself in the situation where you want to write a member function to re-initialize a class back to default values. Because you probably already have a constructor that does this, you may be tempted to try to call the

In Java, is there any way to initialize a field before the super constructor runs? Even the ugliest hacks I can come up with are rejected by the compiler: class Base { Base(String someParameter) { System.out.println(this); } } class Derived extends Base { private final int a; Derived(String someParameter) { super(hack(someParameter, a = getValueFromDataBase())); } private static String hack(String returnValue, int ignored) { return returnValue; } public String toString() { return "a has value " + a; } } Note: The issue disappeared when I switched from inheritance to delegation, but I would