default-value | 易学教程

int array initialization

阅读更多关于 int array initialization

问题 I have here a simple question related to Java. Let's say you have an int array as instance variable: int[] in = new int[5]; So, now by default it contains 5 zeros. But what if you have the same array as local variable. Does it get initialized to zeros? That is not a homework, I am learning Java language. Best regards 回答1: First thing to understand is that, local varibles are stored on stack which are not initialized explicitly with their default values. While instance variables are stored on

How to set default values in Go structs

阅读更多关于 How to set default values in Go structs

问题 There are multiple answers/techniques to the below question: How to set default values to golang structs? How to initialize structs in golang I have a couple of answers but further discussion is required. 回答1: One possible idea is to write separate constructor function //Something is the structure we work with type Something struct { Text string DefaultText string } // NewSomething create new instance of Something func NewSomething(text string) Something { something := Something{} something

Why is the default value of the string type null instead of an empty string?

阅读更多关于 Why is the default value of the string type null instead of an empty string?

问题 It's quite annoying to test all my strings for null before I can safely apply methods like ToUpper() , StartWith() etc... If the default value of string were the empty string, I would not have to test, and I would feel it to be more consistent with the other value types like int or double for example. Additionally Nullable<String> would make sense. So why did the designers of C# choose to use null as the default value of strings? Note: This relates to this question, but is more focused on the

Default value of boolean and Boolean in Java

阅读更多关于 Default value of boolean and Boolean in Java

What are the default values of boolean (primitive) and Boolean (primitive wrapper) in Java? Prince John Wesley The default value for a Boolean (object) is null . The default value for a boolean (primitive) is false . Peter Lawrey The default value of any Object , such as Boolean , is null . The default value for a boolean is false. Note: Every primitive has a wrapper class. Every wrapper uses a reference which has a default of null . Primitives have different default values: boolean -> false byte, char, short, int, float -> 0 float, double -> 0.0 Note (2): void has a wrapper Void which also

Setting the default value of a C# Optional Parameter

阅读更多关于 Setting the default value of a C# Optional Parameter

问题 Whenever I attempt to set the default value of an optional parameter to something in a resource file, I get a compile-time error of Default parameter value for 'message' must be a compile-time constant. Is there any way that I can change how the resource files work to make this possible? public void ValidationError(string fieldName, string message = ValidationMessages.ContactNotFound) In this, ValidationMessages is a resource file. 回答1: No, you will not be able to make the resource work

Python constructor and default value [duplicate]

阅读更多关于 Python constructor and default value [duplicate]

问题 This question already has answers here : “Least Astonishment” and the Mutable Default Argument (31 answers) Closed last year . Somehow, in the Node class below, the wordList and adjacencyList variable is shared between all instances of Node. >>> class Node: ... def __init__(self, wordList = [], adjacencyList = []): ... self.wordList = wordList ... self.adjacencyList = adjacencyList ... >>> a = Node() >>> b = Node() >>> a.wordList.append("hahaha") >>> b.wordList ['hahaha'] >>> b.adjacencyList

Setting Function Defaults R on a Project Specific Basis

阅读更多关于 Setting Function Defaults R on a Project Specific Basis

问题 Commonly, I use the same function settings. I'm wondering if there is a method, other than having a new object in the path that is essentially a wrapper for the function, to set default arguments. For example: paste() has it's sep argument set to a space =" " , I'm tired of writing ,sep="" over and over. So is there a way to "temporarily" replace the function with my chosen defaults? paste(...,sep="") Can I accomplish this through packaging? I've sometimes noticed that, some packages force

Default Values and Initialization in Java

阅读更多关于 Default Values and Initialization in Java

Based on my reference , primitive types have default values and Objects are null. I tested a piece of code. public class Main { public static void main(String[] args) { int a; System.out.println(a); } } The line System.out.println(a); will be an error pointing at the variable a that says variable a might not have been initialized whereas in the given reference, integer will have 0 as a default value. However, with the given code below, it will actually print 0 . public class Main { static int a; public static void main(String[] args) { System.out.println(a); } } What could possibly go wrong

Returning a default value. (C#)

阅读更多关于 Returning a default value. (C#)

问题 I'm creating my own dictionary and I am having trouble implementing the TryGetValue function. When the key isn't found, I don't have anything to assign to the out parameter, so I leave it as is. This results in the following error: "The out parameter 'value' must be assigned to before control leaves the current method" So, basically, I need a way to get the default value (0, false or nullptr depending on type). My code is similar to the following: class MyEmptyDictionary<K, V> : IDictionary<K

C++ template function default value

阅读更多关于 C++ template function default value

问题 Is it possible to define the default value for variables of a template function in C++? Something like below: template<class T> T sum(T a, T b, T c=????) { return a + b + c; } 回答1: Try this: template<class T> T sum(T a, T b, T c=T()) { return a + b + c; } You can also put in T(5) if you are expecting an integral type and want the default value to be 5. 回答2: It all depends on the assumptions that you can do about the type. template <typename T> T sum( T a, T b, T c = T() ) { return a+b+c; }