What is reflection, and why is it useful? I’m particularly interested in Java, but I assume the principles are the same in any language. 2 23 The name reflection is used to describe code which is able to inspect other code in the same system (or itself). For example, say you have an object of … Read more
There have been several questions already posted with specific questions about dependency injection, such as when to use it and what frameworks are there for it. However, What is dependency injection and when/why should or shouldn’t it be used? 3 38
The name reflection is used to describe code which is able to inspect other code in the same system (or itself). For example, say you have an object of an unknown type in Java, and you would like to call a ‘doSomething’ method on it if one exists. Java’s static typing system isn’t really designed … Read more
Is null an instance of anything? No, there is no type which null is an instanceof. 15.20.2 Type Comparison Operator instanceof RelationalExpression: RelationalExpression instanceof ReferenceType At run time, the result of the instanceof operator is true if the value of the RelationalExpression is not null and the reference could be cast to the ReferenceType without raising a ClassCastException. Otherwise the result is false. This means that for any type E and R, for any E … Read more
Referring more generally to the Container pattern (of which an enterprise Java container could be considered a specialization), the book Server Component Patterns by M.Volter, et al. offers the following: [A CONTAINER provides] an execution environment that is responsible for adding the technical concerns to the COMPONENTS…Conceptually, it wraps the COMPONENTS, thus giving clients the … Read more
JLS-8.3.1.1. static Fields says (in part) A static field, sometimes called a class variable, is incarnated when the class is initialized (§12.4). JLS-4.12.4. final Variables says (in part) A constant variable is a final variable of primitive type or type String that is initialized with a constant expression (§15.28) tl;dr Putting that together, a class constant is a static final field.
