static-initializer

I saw it suggested on a blog that the following was a reasonable way to do a "reverse-lookup" using the getCode(int) in a Java enum: public enum Status { WAITING(0), READY(1), SKIPPED(-1), COMPLETED(5); private static final Map<Integer,Status> lookup = new HashMap<Integer,Status>(); static { for(Status s : EnumSet.allOf(Status.class)) lookup.put(s.getCode(), s); } private int code; private Status(int code) { this.code = code; } public int getCode() { return code; } public static Status get(int code) { return lookup.get(code); } } To me, the static map and the static initializer both look like

I have come across a situation where my program hangs, looks like deadlock. But I tried figuring it out with jconsole and visualvm, but they didn't detect any deadlock. Sample code: public class StaticInitializer { private static int state = 10; static { Thread t1 = new Thread(new Runnable() { @Override public void run() { state = 11; System.out.println("Exit Thread"); } }); t1.start(); try { t1.join(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println("exiting static block"); } public static void main(String...strings) { System.out

given the following code: public static class Helpers { private static Char[] myChars = new Char[] {'a', 'b'}; private static Int32 myCharsSize = myChars.Length; } Is it guaranteed that myChars will be initialized before I use its length to assign to myCharsSize ? Yes, they will, please see 10.4.5.1 Static field initialization : The static field variable initializers of a class correspond to a sequence of assignments that are executed in the textual order in which they appear in the class declaration. If a static constructor (Section 10.11) exists in the class, execution of the static field

I'm using a static code block to initialize some controllers in a registry I have. My question is therefore, can I guarantee that this static code block will only absolutely be called once when the class is first loaded? I understand I cannot guarantee when this code block will be called, I'm guessing its when the Classloader first loads it. I realize I could synchronize on the class in the static code block, but my guess is this is actually what happens anyway? Simple code example would be; class FooRegistry { static { //this code must only ever be called once addController(new

Why doesn't Java allow to throw a checked exception from a static initialization block? What was the reason behind this design decision? Kosi2801 Because it is not possible to handle these checked exceptions in your source. You do not have any control over the initialization process and static{} blocks cannot be called from your source so that you could surround them with try-catch. Because you cannot handle any error indicated by a checked exception, it was decided to disallow throwing of checked exceptions static blocks. The static block must not throw checked exceptions but still allows