cloneable


Why doesn't CopyOnWriteArraySet implement the Cloneable interface, while CopyOnWriteArrayList does?

寵の児 提交于 2020-01-01 07:11:08
问题 In this bug report, Doug Lea writes (referring to a pre-release version of JDK 5.0): While CopyOnWriteArraySet is declared Cloneable , it fails to define public clone method. But it eventually ends up that CopyOnWriteArraySet doesn't implement the Cloneable interface at all! (This is true in Java SE 6, 7, and 8.) How is CopyOnWriteArraySet different from CopyOnWriteArrayList with respect to cloning? There is a sound reason nobody ever wants to clone it? P.S. I understand that clone() is not

Implementing a Deck of Cards in Java

跟風遠走 提交于 2019-12-25 12:25:14
问题 So I have a lab (we are allowed to seek outside help on it, so here I am after lots of head scratching) where we have to implement a deck of cards. We have to use the enum class to create num For Suits: public enum Suits { CLUBS, HEARTS, DIAMONDS, SPADES } For Numerals: public enum Numerals { DEUCE(2), THREE(3), FOUR(4), FIVE(5), SIX(6), SEVEN(7), EIGHT(8), NINE(9), TEN(10), JACK(11), QUEEN(12), KING(13), ACE(14); } My card class is pretty straightforward, but I'm not sure about these two

Pretty HABTM List Entry

非 Y 不嫁゛ 提交于 2019-12-25 03:50:23
问题 I have a Recipe, Item, and Units table/model. I have a HABTM relationship with Recipe and Item, and I get the default multiple-select box when adding/editing Recipe. (am using Bake for everything for the most part). The problem is I need to associate quantities and units with each Item. Sample of UI I'm hoping for: A big component of it is the ability to add/delete/edit the individual items. I imagine looking at the submitted form data, and using some jquery and clone would work. But I was

How to use Cloneable type as parameter to Java generic class

社会主义新天地 提交于 2019-12-23 17:58:41
问题 I have a generic class that needs to be able to clone objects of the parameter type. A very simple example is below. The compiler claims clone() from the type Object is not visible. public class GenericTest<T extends Cloneable> { T obj; GenericTest(T t) { obj = t; } T getClone() { // "The method clone() from the type Object is not visible." return (T) obj.clone(); } } I'd prefer not to have the caller do the cloning since there are other things that have to happen to maintain the integrity of

Why shouldn't an object be cloneable? [closed]

☆樱花仙子☆ 提交于 2019-12-23 16:41:06
问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 6 years ago . I read lots of threads about the clone() method of Object and the Cloneable Interface but I couldn't find a legitimate answer to my

Java's “clone()” method generator for Eclipse Galileo

你离开我真会死。 提交于 2019-12-23 07:57:15
问题 What is the best tool for java's clone() method generation in Eclipse Galileo available from repositories? What is the reason, that prevents Eclipse developers from including this tool in standard release? 回答1: It's very hard to implement clone() right. It is considered not a good practice to do so. Bloch (Effective Java) suggest that using clone() should be avoided. Use other means of shallow cloning, like copy-constructors or utilities like commons-beanutils. 回答2: I absolutely agree with

Java's “clone()” method generator for Eclipse Galileo

╄→гoц情女王★ 提交于 2019-12-23 07:57:03
问题 What is the best tool for java's clone() method generation in Eclipse Galileo available from repositories? What is the reason, that prevents Eclipse developers from including this tool in standard release? 回答1: It's very hard to implement clone() right. It is considered not a good practice to do so. Bloch (Effective Java) suggest that using clone() should be avoided. Use other means of shallow cloning, like copy-constructors or utilities like commons-beanutils. 回答2: I absolutely agree with

Does cloning provide a performance improvement over constructors/factory methods?

南楼画角 提交于 2019-12-22 05:05:14
问题 I'm maintaing an older Java code base (jvm 1.4) that seems to use cloning as an alternative to object instantiation, I'm guessing as a performance optimization. Here's a contrived example: public class Foo { private SomeObject obj; // SomeObject implements Cloneable public Foo() { obj = new SomeObject(); obj.setField1("abc"); // these fields will have the same value every time obj.setField2("def"); } public void doStuff() { SomeObject newObj = obj.clone(); // clone it instead of using a

Why Object clone() method available only to classes that implement Cloneable interface? [duplicate]

℡╲_俬逩灬. 提交于 2019-12-20 10:04:14
问题 This question already has answers here : Why is the clone() method protected in java.lang.Object? (11 answers) Closed 6 years ago . I know that clone() is a protected method, but "protected" means that it is accessible for all subclasses of particular class. Any Java class is a subclass of Object , so what is the reason for the protected method here? And why can we call clone() only on classes that implement the Cloneable interface? I can't understand how it connects to the fact that clone()

Invalid covariant type with CRTP clonable class

只愿长相守 提交于 2019-12-18 08:29:24
问题 I'm trying to implement a Clonable class with the CRTP. However, I need to have abstract class that have a pure virtual clone method, overridden by child classes. To make this happen, I need the clone function to return a covariant return type. I made this code below, and the compiler shout at me this error: main.cpp:12:5: error: return type of virtual function 'clone' is not covariant with the return type of the function it overrides ('B *' is not derived from 'AbstractClonable *') The class

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