static-initialization – Tarik Billa

static initialization in interface

May 13, 2023 by Tarik

Interfaces should not have side-effects and that even applies to static intializers. They would have highly JVM-implementation dependent behavior. Look at the following code public class InterfaceSideEffects { public static void main(String[] args) { System.out.println(“InterfaceSideEffects.main()”); Impl i=new Impl(); System.out.println(“Impl initialized”); i.bla(); System.out.println(“Impl instance method invoked”); Foo f=new Impl(); System.out.println(“Impl initialized and assigned to Foo”); f.bla(); … Read more

Why isn’t a qualified static final variable allowed in a static initialization block?

April 25, 2023 by Tarik

The JLS holds the answer (note the bold statement): Similarly, every blank final variable must be assigned at most once; it must be definitely unassigned when an assignment to it occurs. Such an assignment is defined to occur if and only if either the simple name of the variable (or, for a field, its simple … Read more

How to fill a Javascript object literal with many static key/value pairs efficiently?

April 2, 2023 by Tarik

In ES2015 a.k.a ES6 version of JavaScript, a new datatype called Map is introduced. let map = new Map([[“key1”, “value1”], [“key2”, “value2”]]); map.get(“key1”); // => value1 check this reference for more info.

Java: When is a static initialization block useful?

December 19, 2022 by Tarik

A static initialization blocks allows more complex initialization, for example using conditionals: static double a; static { if (SomeCondition) { a = 0; } else { a = 1; } } Or when more than just construction is required: when using a builder to create your instance, exception handling or work other than creating static … Read more

Is final ill-defined?

October 21, 2022 by Tarik

A very interesting find. To understand it we need to dig into the Java Language Specification (JLS). The reason is that final only allows one assignment. The default value, however, is no assignment. In fact, every such variable (class variable, instance variable, array component) points to its default value from the beginning, before assignments. The … Read more