44 lines
1.5 KiB
Plaintext
44 lines
1.5 KiB
Plaintext
Project "shapes"
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Authors: Michael Kolling and David J. Barnes
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This project is part of the material for the book
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Objects First with Java - A Practical Introduction using BlueJ
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David J. Barnes and Michael Kolling
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Pearson Education, 2002
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It is discussed in chapter 1.
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This is a very simple project to demonstrate some characteristics of
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objects.
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You can create various shapes, and you will see, if you do, that those
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shapes are drawn on screen (in a window that we call the "canvas").
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You can then manipulate these objects: change their position, size and
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colour. Try it out: create a few different squares, triangles and circles.
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This project is designed as a first example of object-oriented programming.
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It illustrates a number of concepts:
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- a Java project (application) is a collection of classes
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- objects can be created from classes
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- from any one class, many objects may be created
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- objects have operations (methods)
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- operations can have parameters
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- parameters have types (at least String and int)
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- objects hold data (fields)
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- the operations and fields are common to all objects
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- the values stored in the fields can be different for each object
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The project also demonstrates
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- BlueJ object creation
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- interactive method invocation
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- parameter passing
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A good second project to look at after this is "picture", which adds a class
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to those ones in this project. That class (named "Picture") uses the shapes
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to draw a picture. It can be used to experiment with coding.
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Michael Kolling, July 2000 |