If you have a singleton class and you run two webapps that use this class in Tomcat both webapps will get 2 different instances of this singleton in JVM running the Tomcat. But if your webapp will use a singleton from JRE or Tomcat shared libs, eg Runtime.getRuntime webapps will get the same instance of … Read more
A DB connection should not normally be a Singleton. Two reasons: many DB drivers are not thread safe. Using a singleton means that if you have many threads, they will all share the same connection. The singleton pattern does not give you thread saftey. It merely allows many threads to easily share a “global” instance. … Read more
You would make that a module-level variable. For example, // In foo.js define(function () { var theFoo = {}; return { getTheFoo: function () { return theFoo; } }; }); // In bar.js define([“./foo”], function (foo) { var theFoo = foo.getTheFoo(); // save in convenience variable return { setBarOnFoo: function () { theFoo.bar = “hello”; … Read more
Remove db.close(); If you try another operation after closing the database, it will give you that exception. The documentation says: Releases a reference to the object, closing the object… Also, check out Android SQLite closed exception about a comment from an Android Framework engineer which states that it is not necessary to close the database … Read more
Josh Bloch recommends using a single-element enum type to implement singletons (see Effective Java 2nd Edition, Item 3: Enforce the singleton property with a private constructor or an enum type). Some people think this is a hack, since it doesn’t clearly convey intent, but it does work. The following example is taken straight from the … Read more
This question might be old but since this was the nearest answer I found when I had this problem I though I’d describe my solution. Using JUnit 4 Split your tests up so that there is one test method per class (this solution only changes classloaders between classes, not between methods as the parent runner … Read more
If I’m not wrong, you can cancel the closing event of that window and instead set visibility to hidden private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs e) { e.Cancel = true; this.Visibility = Visibility.Hidden; }
(1) UPDATE 2019: ES7 Version class Singleton { static instance; constructor() { if (instance) { return instance; } this.instance = this; } foo() { // … } } console.log(new Singleton() === new Singleton()); (2) ES6 Version class Singleton { constructor() { const instance = this.constructor.instance; if (instance) { return instance; } this.constructor.instance = this; } … Read more
Yes, it has singleton pattern, Code to create a singleton object, public partial class Form2 : Form { ….. private static Form2 inst; public static Form2 GetForm { get { if (inst == null || inst.IsDisposed) inst = new Form2(); return inst; } } …. } Invoke/Show this form, Form2.GetForm.Show();
The standard singleton pattern is: final class Manager { static let shared = Manager() private init() { … } func foo() { … } } And you’d use it like so: Manager.shared.foo() Credit to appzYourLife for pointing out that one should declare it final to make sure it’s not accidentally subclassed as well as the … Read more