methods | 易学教程

Is static method in JAVA creates a single instance?

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I have a doubt. Suppose in a multithreaded environment 10K users are using a site simultaniously and the site has a static method. If a static method in JAVA creates a single instance, then the 10k-th user needs to wait for the method until rest of the users complete their usage. Am I right? Can anybody please explain? If a static method in JAVA create a single instance, then 10K th user need to wait for the method untill rest of the usres complete there usage. Calling a static method doesn't create an instance implicitly. You can do so within the method, of course - but you don't have to. Nor

Can't call a method from another window in C# WPF

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问题 Ok, let's say I have two windows. In the first one I have a method public void Test() { Label.Content += " works"; } And in the second one I call this method: MainWindow mw = new MainWindow(); mw.Test(); But nothing happens. What am I doing wrong? Thanks. 回答1: You can assign the Owner to the window that was created in your MainWindow. window.Owner = this; //This is added to the code that use to create your Window Then you should be able to access it something like this. ((MainWindow)this

Calling method on child class from parent class method (Objective-c 2.0)

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问题 I have experience with object-oriented programming however this situation is unfamiliar for some reason. Consider the following Objective-c 2.0 code: @interface A : NSObject @end @implementation A - (void) f { [self g]; } @end @interface B : A @end @implementation B - (void) g { NSLog(@"called g..."); } @end Is this the correct way to call a method on a child class from a method in the parent class? What happens if another child class doesn't implement method g ? Perhaps there's a better way

Forcing two parameters of a generic method to have the same concrete type

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问题 How can I have a method with two parameters, with both parameters having the same concrete type? For example, boolean equals(Object a, Object b) allows for a of any type and b of any type. I want to force such that a and b have the same concrete type. I tried <T> boolean equals(T a, T b) and inputting a Date and a String to that method, expecting a compile-time error, but I get no errors, since T will resolve to ? extends Serializable & Comparable , since both Date and String implements

How to retrieve the current method name so to output it to the logger file?

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问题 I am using Ruby on Rails 3.2.2 and, in order to display warning messages for development purposes, I am using logger.warn in my code. I would like to retrieve the method name in which that logger.warn runs so to output that method name to the log file. class ClassName < ActiveRecord::Base def method_name # Note: This code doesn't work. It is just a sample. logger.warn "I would like to retrieve and display the #{self.class.to_s}##{method_name}" end end In the log file I would like to see: I

Easy way of overriding default methods in custom Python classes?

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问题 I have a class called Cell: class Cell: def __init__(self, value, color, size): self._value = value self._color = color self._size = size # and other methods... Cell._value will store a string, integer, etc. (whatever I am using that object for). I want all default methods that would normally use the "value" of an object to use <Cell object>._value so that I can do: >>> c1 = Cell(7, "blue", (5,10)) >>> c2 = Cell(8, "red", (10, 12)) >>> print c1 + c2 15 >>> c3 = Cell(["ab", "cd"], "yellow",

How to insert a method inside a LINQ lambda extension method

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I have to place a method inside a LINQ lambda. I have the following code: string productName = "Some product"; searchShoppingCart = shoppingCart.Where(m => productName.Equals(_ProductRepository.GetProductName(m.Id))); Basically this code is used to select all the shoppingCart instances that contain productName . The method string GetProductName(int shoppingCartId) is a method from _ProductRepository that returns the name of one product. How this method is implemented and its logic does not matter. The problem is that LINQ throws an exception . I know the reasons why this exception is thrown, I

c# generic method overload not consistent with abstract Visitor pattern

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问题 experimenting with Visitor pattern and generic method I found a kind of discrepancy in C#.NET. AFAIK C# compiler prefers an explicit overload to a generic method, therefore the following code: public abstract class A { public abstract void Accept(Visitor v); } public class B : A { public override void Accept(Visitor v) { v.Visit(this); } } public class C : A { public override void Accept(Visitor v) { v.Visit(this); } } public class D : A { public override void Accept(Visitor v) { v.Visit(this

Android: vibrator method (if phone has no vibrator?)

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问题 I want to use the vibrator method in my app, and i have got it working on my phone which has a vibrator which is great. however phones that don't have a vibrator what happens. does it not work at all? does it stop the app working? or does it not show up in the market at all? or do i have to ask the phone if it has a vibrator? I would also like to know if this code is good or needs any adjustments? here is my code.. Vibrator vi; vi = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE); vi

How can additional data be associated with existing objects using extension methods?

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问题 Since .NET Framework 3.5, developers have been able to add extension methods callable from instances of any object type. Extension properties have not been implemented in C#, however. Unlike extension methods, extension properties would involve storing some extra state information for individual objects. However, even for extension methods, it would be highly useful in some programming scenarios to be able to access after-added/extension information for the objects on which those extension