For example the following program prints 1 then This is because the default copy assignment operator copies the raw pointer to b2. In short, we should be aware that copying and initialization objects are our responsibility. Skip to content. Change Language. Related Articles. Table of Contents. Save Article. Improve Article. Like Article. Base base;. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. How Many default methods does a class have? Ask Question. Asked 11 years ago. Active 6 years, 1 month ago. Viewed 34k times. Sorry, this might seem simple, but somebody asked me this, and I don't know for certain. Constructor, Copy Constructor, Assignment, Destructor?
Is that it? Or are there more? Improve this question. Martin B Its been asked to me in 3 interviews now. Add a comment. Active Oldest Votes. Defined when used Copy constructor - declared only if the user hasn't declared one. Improve this answer. Armen Tsirunyan Armen Tsirunyan k 54 54 gold badges silver badges bronze badges. There are concerns that having them implicitly declared may break legacy code.
I should think having a reference as a member variable would prevent generation of the default assignment operator, not cause problems with the copy constructor. James: That sounds very interesting. Could you perhaps provide a link to discussion of this topic? They are both listed in the October mailing on the WG21 website. I haven't had time to read either of them yet; Anthony Williams has a brief summary of the issues to be discussed at Batavia on his blog.
I haven't had time to read Stroustrup's paper yet, but the one by Abrahams made a pretty convincing case for no implicit move functions. Still, it'll be interesting to see how it turns out.
It would be nice if they could get implicit move working without breaking existing code, but it seems like there's no obvious way to do it. The following example defines a static method that retrieves a ZoneId object corresponding to a time zone identifier; it uses the system default time zone if there is no ZoneId object corresponding to the given identifier.
As a result, you can simplify the method getZonedDateTime :. Like static methods in classes, you specify that a method definition in an interface is a static method with the static keyword at the beginning of the method signature. All method declarations in an interface, including static methods, are implicitly public , so you can omit the public modifier.
Default methods enable you to add new functionality to existing interfaces and ensure binary compatibility with code written for older versions of those interfaces. In particular, default methods enable you to add methods that accept lambda expressions as parameters to existing interfaces. This section demonstrates how the Comparator interface has been enhanced with default and static methods.
This example rewrites the Card and Deck classes as interfaces. The Card interface contains two enum types Suit and Rank and two abstract methods getSuit and getRank :. The class StandardDeck implements the abstract method Deck. The method Collections. The member entireDeck is an instance of List whose elements are of the type Card , which extends Comparable.
The class PlayingCard implements the Comparable. The method compareTo causes the method StandardDeck. What if you want to sort the deck first by rank, then by suit? You can define the following method in the class StandardDeck :. With this method, you can specify how the method Collections. One way to do this is to implement the Comparator interface to specify how you want the cards sorted.
However, this approach is too verbose; it would be better if you could specify just the sort criteria and avoid creating multiple sorting implementations. Suppose that you are the developer who wrote the Comparator interface. What default or static methods could you add to the Comparator interface to enable other developers to more easily specify sort criteria? To start, suppose that you want to sort the deck of playing cards by rank, regardless of suit.
You can invoke the StandardDeck. Because the interface Comparator is a functional interface , you can use a lambda expression as an argument for the sort method.
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