In a procedural program, the code is king and the data is subordinate. In other words, you have programs which act on data and they’re not usually tightly bound. In the OO world, objects are the primary thing of interest. An object consists of data and the code that is allowed to act on that … Read more
One of the best ways would be using the enum polymorphism technique: public class EnumTest { public enum Foo { A { @Override public Bar getBar() { return Bar.Alpha; } }, B { @Override public Bar getBar() { return Bar.Delta; } }, C { @Override public Bar getBar() { return Bar.Alpha; } }, ; public … Read more
The diamond problem only applies to implementation inheritance (extends in all versions of Java prior to Java 8). It doesn’t apply to API inheritance (implements in all versions of Java prior to Java 8). Since interface methods with matching type signatures are compatible, there is no diamond problem if you inherit the same method signature … Read more
I wouldn’t waste my time thinking whether the lambda expressions are a violation of OO principles. Its goal is to increase the power of a language and not to write an OO code, I don’t see how lambdas can violate encapsulation, inheritance or polymorphism. This article explains how Java handles lambda expressions: What’s interesting about … Read more
For reference types, == checks whether the references are equal, i.e. whether they point to the same object. For primitive types, == checks whether the values are equal. java.lang.Integer is a reference type. int is a primitive type. Edit: If one operand is of primitive type, and the other of a reference type that unboxes … Read more
Wrapping any piece of code in a try/catch block without a good reason is bad practice. In the .NET programming model, exceptions should be reserved for truly exceptional cases or conditions. You should only try to catch exceptions that you can actually do something about. Furthermore, you should should hardly ever catch the base System.Exception … Read more
Yes you can do this, but since you’re asking, I have to ask: Are you absolutely sure that you need to? (If you say “yes”, then go back, figure out what you want to do, and see if there’s a different way to do it) However, if you really want to inject storage into a … Read more
No – “is a” does not always lead to inheritence. A well cited example is the relationship between a square and a rectangle. A square is a rectangle, but it will be bad to design code that inherits a Square class off a Rectangle class. My suggestion is to enhance your “is a / has … Read more
Encapsulation and information hiding are very closely linked concepts, though their precise definitions vary depending on who you talk to. The concept of “information hiding” was first described by Parnas (1972) who suggested that access to information should be restricted to reduce the interconnectedness of a system. He proposed that this would facilitate splitting of … Read more
No – this would violate Liskov’s Substitution Principle. You should always be able to use an instance of a subtype as if it were an instance of a supertype. Don’t forget that a caller may only be aware of your type “as” the base type or an interface. Consider this code: object foo = new … Read more