2 classes and objects

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Object Oriented¶

What do you like about OO? Some people say...

• It helps me design in a more natural way. Things have a way of evolving.
• Not messing around with the code I've already tested, just to add a new feature.
• Reusing code in other applications. When I write a new class, I can make it flexible enough to be used in something new, later

Class¶

A class describes what an object knows(instance variables, 实例变量) and what an object does(methods).

What's the difference between a class and an object?

• A class is not an object.
• A class is the blueprint for an object.
• A class tells the JVM how to make an object of that particular type.
• Each object made from that class have its own values for the instance variables of that class.

main method¶

The two uses of main method:

• to test your real class
• to launch/start your Java application.