• What is your weight?
Together, the concepts of state and string allow you to say to Person: tell me who you are by giving me a listing (or String) of your attributes.
Section 6. Principles of OOP
On the Java platform, you can use access specifiers (which I'll introduce later in the tutorial) to vary the nature of object relationships from public to private. Public access is wide open, whereas private access means the object's attributes are accessible only within the object itself.
The public/private boundary enforces the object-oriented principle of encapsulation. On the Java platform, you can vary the strength of that boundary on an object-by-object basis, depending on a system of trust. Encapsulation is a powerful feature of the Java language.
In structured programming, it is common to copy a structure, give it a new name, and add or modify the attributes that make the new entity (such as an Account record) different from its original source. Over time, this approach generates a great deal of duplicated code, which can create maintenance issues.
OOP introduces the concept of inheritance, whereby specialized objects — without additional code — can "copy" the attributes and behavior of the source objects they specialize. If some of those attributes or behaviors need to change, then you simply override them. You only change what you need to change in order to create specialized objects. As you know from the Object-oriented programming concepts section, the source object is called the parent, and the new specialization is called the child.
You'll see plenty of examples of inheritance in Java programming later in the tutorial, especially in .