So i was playing around in java once again and while doing so, i ran into an interesting problem.
I was trying to write my self a little registration service. If an object of a certain type is instantiated via its constructor it would retrieve an id from my registration service and is added to the services list of objects.
Here is an example object
public class Test {
private final Long id;
public Test() {
this.id = TestRegistration.register(this);
throw new IllegalAccessError();
}
public Long getId() {
return this.id;
}
}
And here is an example service
public class TestRegistration {
private final static Map<Long, Test> registration = new HashMap<>();
protected final static long register(final Test pTest) {
if (pTest.getId() != null) {
throw new IllegalStateException();
}
long freeId = 0;
while (registration.containsKey(freeId)) {
freeId = freeId + 1;
}
registration.put(freeId, pTest);
return freeId;
}
protected final static Test get(final long pId) {
return registration.get(pId);
}
}
Now as you can see, the constructor of my class Test can't successfully execute at all since it always throws an IllegalAccessError. But the method register(...) of my TestRegistration class is called in the constructor before this error is thrown. And inside this method it is added to the registrations Map. So if i would run for example this code
public static void main(final String[] args) {
try {
final Test t = new Test();
} catch (final IllegalAccessError e) {
}
final Test t2 = TestRegistration.get(0);
System.out.println(t2);
}
My TestRegistration does in fact contain the object created when the constructor of my Test class was called and i can (here using variable t2) access it, even tho it wasn't successfully created in the first place.
My question is, can i somehow detect from within my TestRegistration class if the constructor of Test was executed successfully without any exceptions or other interruptions?
And before you ask why i throw this exception in the first place here is my answer. Test may have potential subclasses i don't know of yet but still will be registered in my TestRegistration class. But since i don't have influence on the structure of those subclasses i can't tell if their constructor will throw an exception or not.
