effective-java – Tarik Billa

Understanding the concept behind Service provider framework like JDBC using the factory method

November 28, 2023 by Tarik

Consider something like the following: public interface MyService { void doSomething(); } public class MyServiceFactory { public static MyService getService() { try { (MyService) Class.forName(System.getProperty(“MyServiceImplemetation”)).newInstance(); } catch (Throwable t) { throw new Error(t); } } } With this code, your library doesn’t need to know about the implementations of the service. Users of your library … Read more

What does “Recursive type bound” in Generics mean?

September 29, 2023 by Tarik

To understand the concept of recursive type bounds, let’s solve a simple problem. This concept is easier to understand by solving a real problem. I’ll provide the definition of the recursive type bound at the end, because it makes more sense after understanding the concept. Problem Assume that we have to sort the fruits by … Read more

Why are readObject and writeObject private, and why would I write transient variables explicitly?

August 14, 2023 by Tarik

(1) The methods are not declared in any class or interface. A class, that implements the Serializable interface and requires special special handling during the serialization and deserialization process must implement those methods and the serializer/deserializer will try to reflect those methods. This is one of the rather strange corners in Java where the API … Read more

Why are public static final array a security hole?

July 28, 2023 by Tarik

Declaring static final public fields is usually the hallmark of a class constant. It’s perfectly fine for primitive types (ints, doubles etc..), and immutable classes, like strings and java.awt.Color. With arrays, the problem is that even though the array reference is constant, the elements of the array can still be changed, and as it’s a … Read more

What is an AssertionError? In which case should I throw it from my own code?

January 30, 2023 by Tarik

Of course the “You shall not instantiate an item of this class” statement has been violated, but if this is the logic behind that, then we should all throw AssertionErrors everywhere, and that is obviously not what happens. The code isn’t saying the user shouldn’t call the zero-args constructor. The assertion is there to say … Read more