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Questions tagged [private-constructor]

73 questions
52
votes
7 answers

private constructor

Possible Duplicate: What is the use of making constructor private in a class? Where do we need private constructor? How can we instantiate a class having private constructor?
Atul
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How to instantiate an object with a private constructor in C#?

I definitely remember seeing somewhere an example of doing so using reflection or something. It was something that had to do with SqlParameterCollection which is not creatable by a user (if I'm not mistaken). Unfortunately cannot find it any…
User
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4 answers

Scala case class private constructor but public apply method

If I have the following case class with a private constructor and I can not access the apply-method in the companion object. case class Meter private (m: Int) val m = Meter(10) // constructor Meter in class Meter cannot be accessed... Is there a…
Erik
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4 answers

Difference between java enum with no values and utility class with private constructor

A common thing to do to utility classes is to give them a private constructor: public final class UtilClass { private UtilClass() {} ... } But unfortunately, some tools don't like that private constructor. They may warn that it's never…
Craig Gidney
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37
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1 answer

abstract class vs private constructor

I have a java class which has only static methods and fields, so I don't want any object to be created for that. I can acheive this in two ways, make class abstarct. use private constructor. Which of the two is better way?
user3104091
27
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7 answers

Which is the difference between declaring a constructor private and =delete?

For example, I want to declare a class but I want the client to not be able to use the copy constructor (or copy assignment operator) Both of the following two does not allow the use of the copy constructor: 1. class Track { public: Track(){}; …
Avraam Mavridis
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2 answers

Using private constructor in a macro

I want to use a private constructor in a macro. This example is a positive integer, but the basic pattern could not only be used for other numeric types like even numbers, but also string derived types like email addresses or a directory name. By…
Rich Oliver
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14
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3 answers

Instantiate a derived class object, whose base class ctor is private

How to instantiate a derived class object, whose base class ctor is private? Since the derived class ctor implicitly invokes the base class ctor(which is private), the compiler gives error. Consider this example code below: #include…
nitin_cherian
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6 answers

JaCoCo and missed coverage of private default constructor

I'd like to see an example to prevent JaCoCo to report private empty constructors as non-covered code in a Java class. In the maven plugin configuration I have CLASS …
mat_boy
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6 answers

Why HTTPServlet is an abstract class? Any functional reason?

HttpServlet is an abstract class with all implemented methods. Why it is abstract? The most common answer I got is, to restrict the instantiation of HttpServlet. But there are other ways of doing it, like a private constructor will restrict the…
rockyPeoplesChamp
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Final class with private constructor, what is the design principle

I was recently going through one of the Netflix open source project There I found use of both final class along with private constructor. I fully aware that final is to avoid inheritance private is to disallow instantiation But m just curious to…
Sudip7
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5 answers

Static Class VS Private Constructor

Today, I have been reading about static class and private constructor. Static Class - We cannot create an instance on the static class. we cannot inherit the static class. Only single instance is generated. Private Constructor - We cannot create an…
KiddoDeveloper
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6 answers

Preventing call of a private constructor from within the class in Java

We can restrict the creation of object of a class by making its constructor private. But this constructor could still be called from within the class. Is there any way to prevent this in Java? Thanks.
code_pro
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3 answers

Private vs Static constructors in .Net

I searched for this a lot, but none of the answers are clear (at-least for me!). Now I'm putting this question in SO, as I believe I can't get a more clarified answer anywhere else. When should I use a private/static constructor in my class? I'm…
Sandeep
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copy constructor is implicitly deleted because the default definition would be ill-formed

I've got a class A (from a library over which I have no control) with a private copy constructor and a clone method, and a class B derived from A. I would like to implement clone for B as well. The naive approach #include class A { // I…
Nico Schlömer
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