methods | 易学教程

How to pass a list of unknown objects of type custom-class containing some properties to method?

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问题 I am making a databasehelper class with methods to access a SQLCE database. I want to use the same method to read row(s) using different classes containing properties that match the fields in the different tables. The class to be used is determined during runtime and I want to pass a list with objects from the class on to the method and get the propertynames and use them to read the database. Would be very handy because I could use it for all my (SQLCE-)databases. (I updated the erroneous

validator method not work in the JSF custom composite components

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问题 JSF custom composite components input.xhtml <cc:interface> <cc:attribute name="validator"/> </cc:interface> <cc:implementation> <h:inputText validator="#{cc.attrs.validator}"/> </cc:implementation> *.xhtml <l:input value = ... validator="#{testValidator.validator}"/> java code @ManagedBean public class TestValidator { public void validator(FacesContext context, UIComponent component, Object value) throws ValidatorException { System.out.println("Call validator"); } } PropertyNotFoundException:

Method chaining without parentheses, how to?

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I would like to do a method chain, for example like this: Car myCar = new Car(); // Chaining myCar.config.engine.cylinders("4"); But how do I do the chaining, without using parentheses in "config" or "engine"? I can only figure out to do it like this: myCar.config().engine().cylinders("4"); Dethariel You can do this by declaring Config property in your Car class. Then Engine property in CarConfig class, like this: public class Car { public CarConfig Config { get; set; } } Then you can chain the calls. You could use properties as many suggest, but this whole thing stinks of breaking the Law of

Is static method in JAVA creates a single instance?

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问题 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? 回答1: 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

In Java, how can I take a variable obtained from a user input from one method and use the output in another method?

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问题 I can't figure out how to bring a variable from one method into another for use, especially that from a user input. For example, this test program doesn't work. How would I make it work? import java.util.*; public class Test { public static void main(String[] args) { input(); output(); } public static void input() { Scanner console = new Scanner(System.in); System.out.print("This number multiplied by 7: "); int number = console.nextInt(); int number7 = number * 7; System.out.print("The result

How to check if a python class has particular method or not?

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问题 class C(Test): def __init__(self): print "in C init" super(C, self).__init__() def setup(self): print "\tin C setup" def runtest(self): print "\t\tin C runtest" def teardown(self): print "\t\t\tin C teardown" I have such classes in different modules. For eg class A , B , C etc.. In one module I'm considering only classes who have setup and teardown methods. Suppose Class A doesn't have setup method, I don't want to consider it for further parth of my program where I'm building list of classes

good name for a method that adds to a container if not aleady there

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问题 What's a good name for a method that adds something to a container if it's not already there, i.e. void AddCustomerToList(CustomerList list, Customer customer) but that name does not properly convey that it won't be added if it's not there already. What is a better name? AddCustomerToListIfNotThereAlready? EnsureCustomerInList? 回答1: AddIfNotPresent 回答2: Change CustomerList to CustomerSet, then it's obvious. add(CustomerSet set, Customer customer); 回答3: bool TryAdd(CustomerList list, Customer

static and non static methods in java [duplicate]

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问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: When should a method be static? i am trying to make an interface class for tube/subway ticket machine. well not for real, but for a coursework in a computer science module. i dont understand when to use static methods. i dont know much about computer sciences, but main methods seem to use static. class UNInterfaceTest { public static final int NOTTING_HILL = 1; public static final int HIGH_KEN = 2; public static

How to insert a method inside a LINQ lambda extension method

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问题 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

Final in method parameter in eclipse

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问题 When I try to put final in method parameter eclipse doesn't help. Any idea how to get this to work? 回答1: I don't think this is possible. The closest thing to this is to set a "save action" which will automatically add final modifiers to method parameters when you save the file. Preferences > Java > Editor > Save Actions 回答2: This probably will be as close as you can get to it. It would be a lot of work to do this for every keyword, but since there is only so many of them it's possible. You