I have written a Java enum where the values have various attributes. These attributes could be stored in any of the following ways: Using fields: Using abstract methods: Using class level map: How should I decide when to prefer which? Thanks! Answer (I am answering my own question so that I can share some thi…
Tag: oop
Comparing two classes by its types or class names
There is need to compare two objects based on class they implement? When to compare using getClass() and when getClass().getName()? Is there any difference between this approaches to compare two Objects class types (names)? EDIT 1 What about: ? Answer Is there any difference between this approaches to compare…
Why can attributes in Java be public?
As everybody knows, Java follows the paradigms of object orientation, where data encapsulation says, that fields (attributes) of an object should be hidden for the outer world and only accessed via methods or that methods are the only interface of the class for the outer world. So why is it possible to declar…
Why would you declare an Interface and then instantiate an object with it in Java?
A friend and I are studying Java. We were looking at interfaces today and we got into a bit of an discussion about how interfaces are used. The example code my friend showed me contained this: Where IVehicle is an interface that’s implemented in both the car and bike classes. When defining a method that…
How to use object oriented programming with Hibernate?
While using ORM tools such as Hibernate, I’ve found it is advantageous to keep all business logic out of my business objects and instead keep it in a service layer. The service layer creates the business object POJOs, manipulates them, and uses DAOs to save them. But isn’t this in a way taking a s…
How to do method overloading for null argument?
I have added three methods with parameters: When I am calling doSomething(null) , then compiler throws error as ambiguous methods. So is the issue because Integer and char[] methods or Integer and Object methods? Answer Java will always try to use the most specific applicable version of a method that’s …
The purpose of interfaces continued
OK so I gather that Interfaces are a way to enforce that an object implements a certain amount of functionality, without having to use inheritance. Kind of like a contract. And I semi see the point of them. But if all you have in the interface is: and it has no implementation as such, then whoever uses your i…
Disadvantage of object composition over class inheritance
Most design patten books say we should “Favor object composition over class inheritance.” But can anyone give me an example that inheritance is better than object composition. Answer In Java, whenever you inherit from a class, your new class also automatically becomes a subtype of the original cla…
Why use inheritance at all? [closed]
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String, StringBuffer, and StringBuilder
Please tell me a real time situation to compare String, StringBuffer, and StringBuilder? Answer Mutability Difference: String is immutable, if you try to alter their values, another object gets created, whereas StringBuffer and StringBuilder are mutable so they can change their values. Thread-Safety Differenc…