Beginning Java Objects: Chapter 3
Objects and Classes
Encapsulation
Encapsulation is a formal term referring to the mechanism that bundles together the
state information (attributes) and behavior (methods) of an object into a single logical
unit. Everything that we need to know about a given student is, in theory, contained
within the 'walls' of the student object, either directly as an attribute of that object
or indirectly as a method that can answer a question or make a determination about the
object's state.
Encapsulation is not unique to OO languages, but in some senses is perfected by them. For those of
you familiar with C, you know that:
A C struct(ure) encapsulates data:
struct employee {
char name[30];
int age;
}
and a C function encapsulates logic — data is passed in, operated on, and an answer is optionally
returned:
float average(float x, float y) {
return (x + y)/2.0;
}
But only with OO programming languages is the notion of encapsulating data and behavior in a
single construct called a class, to represent an abstraction of a real-world entity, truly embraced.
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