If there’s really a business reason to cater for the situation where your variable is null, then you the developer should provide an else block. Concerning literature, yes there is actually a performance cost to throwing exceptions, so it’s recommended you avoid your app throwing exceptions as much as possible. You can read more about … Read more
How about MailMessageUtilities or MailMessageFactory? 2 solved How to call a class or what pattern to use? [closed]
The identifier private restricts access to class methods and class friends. The static identifier indicates there is only 1 instance of the variable to be shared among all children. So, private static means a data member that has only one instance, regardless of the number of instances, and only class methods and class friends can … Read more
If you are familiar with UML notation you can just try http://www.w3sdesign.com. Architecture patterns: http://martinfowler.com/eaaCatalog/ 2 solved Popular and useful design patterns [closed]
use a base class instead of an interface: abstract class MyBaseClass { public Dictionary<int,string> dic { get; set; } public MyBaseClass() { dic = new Dictionary<int, string>(5); } public void Add(int key, string value) { dic.Add(key, value); } } public class MyClass1 : MyBaseClass { public MyClass1():base() { } } public class MyClass2 : MyBaseClass … Read more
Regex may complicate the code. If its a simple comparison you could use indexOf instead. Seeing the format of your strings it better to use properties then you have better control over the values. Eg import java.io.IOException; import java.io.StringReader; import java.util.Properties; public class StringToProp { public static void main(String[] args) { String str1 = “property: … Read more
The official source for the Java standard library is the standard Java API documentation. And one notable source for design patterns is the book Design Patterns: Elements of Reusable Object-Oriented Software. To begin with, when you look at the options, the question (as quoted in your post) is badly formulated: “Which of the following classes … Read more
I would choose Factory. With this pattern you can easily create your new object and along with it anything you need. You juste need to pass the right parameters to your service. check these docs for creating Factory pattern in SYmfony https://symfony.com/doc/current/service_container/factories.html solved Where I should put the model creation code? [closed]
I’d suggest using a UI that says loading.., and may be you want to use an AsyncTask or some background threads to load the things and then update the UI and say you’re ready. solved How to start an Android Application without loading Activities immediately? [closed]
File folder = new File(“JavaClassesPath”); ArrayList<String> all = new ArrayList<>(); for (final File fileEntry : folder.listFiles()) { if (!fileEntry.isDirectory()) { all.add(fileEntry.getName().substring(0, fileEntry.getName().lastIndexOf(‘.’))); } } String className = “PackageName”; for (String s: all) { if (!s.equals(“AbstractClassName”)) { Class<?> clazz = Class.forName(className + ‘.’ + s); Constructor<?> ctor = clazz.getConstructor(); Object object = ctor.newInstance(); allHandlers.add((RequestHandler) object); } … Read more
The main difference between a Singleton and a Class with a bunch of Class methods is that the Singleton can preserve some kind of state. For example, an array of data or some boolean flags. By calling sharedInstance, you access to the one and only instance of this class, that is being kept alive(and the … Read more
Interpreter pattern is used to interpreter a (domain) language defined with grammatical rules. Mediator is used when it is hard to achieve synchronization among the lot of objects, then communication goes via mediator. Hope that this helps. solved What is the difference between interpreter and mediator design pattern? [closed]
I have adapted the java example from the wikipedia article: In this example we have different roles, each having a fixed purchasing limit and a successor. Every time a user in a role receives a purchase request that exceeds his or her limit, the request is passed to his or her successor. A builder allow … Read more
Check out Math.random(), which gives you a random number [0,1). You want false 3/100 times, so if you multiply your random number by 100, your range will become [0, 100). Then just check if the random number is less than 3, if so, return false. 5 solved I want to return a value of true … Read more
It strikes me that there is a much simpler solution that doesn’t involve explicit semaphores and custom code (and bugs). Just use a bounded BlockingQueue (javadoc) and have the threads use put(…) to add items to the queue. When queue is full, put will block the thread that is calling it … until queue space … Read more