BRINGING THE PIECES TOGETHER II – Interface Declaration and Implementation

In my last post, we started bringing together the pieces of our previous tutorials together – we were able to set up our IDEs, created packages, classes, variables and Identifiers. In this post, we will continue from where we stopped which was the class. Looking again at the structure of our application (AreaofShapes) as we discussed earlier here, we have three packages, nine (9) classes and one (1) interface altogether as shown below.


In the last lesson, I explained the purpose of each package and we saw the content of ShapeVariableBean and how encapsulation came to play. Today, we will focus more on the package and also, we will see how other classes implements interface within this package. In package, the shapes are divided into two; PolygonController and NonpolygonController.

Note: As an update on the last post, I added a new item on this package which is what we will be focusing on today. I added interface AllShapesInterface above so we can see how to make use of an interface in the course of these set of lessons. Before we continue, please refer to my earlier post on interface where I explained in detail what an Interface is in case you missed the lesson.

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Java Modifiers…

A modifier just as the name implies is said to transform , change or customize another element in the structure, on which it is dependent. When you think of modifiers, think of the role of an adjective in a phrase- just as adjective modifies a noun in spoken languages, the modifier modifies the element its dependent on. Also, just as a phrase without an adjective can exist without losing its meaning (you can say “a girl” instead of saying “a beautiful girl” ), a Java keyword can exist without a modifier; a modifier only gives more details to its dependent. Java modifiers can be classed into two as listed below with the types under each category

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