Java Object-Oriented Programming: Key Concepts and Terms

abstraction

The process of finding the essential feature set for a building block of a program such as a class.

access specifier

A keyword that indicates the accessibility of a feature, such as private or public. private is only available within the class. public is available to any other program.

accessor method

A method in an object class that will return information about the current state of the object. It may return the exact information of one instance field or a calculated answer based on one or more instance fields. It does NOT modify the instance fields.

actual parameter

The explicit parameter in a method call. Specifies a value that is passed into the formal parameter in the method definition. It can be an initialized variable, String literal or number.

argument

see actual parameter.

black box

The concept of using something without knowing its implementation. A black box is created by encapsulation - the hiding of unimportant details which is done among other places when creating an object class.

constructor

A method that initializes a newly instantiated object. It sets the initial state of the object. A unique method that must have the same name as the class and cannot have ANY return type.

encapsulation

The hiding of implementation details as well as anything private inside the class while still providing a public interface. It is said to be hiding the unimportant details.

explicit parameter

A parameter of a method other than the object on which the method is invoked. It is the values inside the ( ) following the method name in either the method call or the method definition.

formal parameter

The explicit parameter in a method definition. It includes a data type and variable name for each parameter. It receives its value from the actual parameter in the method call.

implement

To write the details of a method or class.—write the statements inside of the method/class body.

implicit parameter

The object on which a method is invoked. For example, in the call x.f(y), the object x is the implicit parameter of the method f.

initialization

Setting a variable to a well-defined value once it is created. You can do this when declaring or later in the code, but it must be done before using the variable in a computation or as a parameter.

instance fields

A variable defined in a class, outside of any method, for which every object of the class has its own value. Should have private access.

instantiate

create & initialize an instance of an Object - example: new ClassName();

javadoc

The documentation generator in the Java SDK.

Documentation comments

Comments that start with /** in Java source files, used to produce linked HTML files for API documents.

Local variable

A variable whose scope is a block, belonging to a method only.

Method body

The container containing the statements that are executed when a method is called.

Method call

A statement that invokes a method, causing a different method to be executed.

Mutator method

A method in an object class that changes the current state of the object, modifying one or more instance fields.

Object-oriented design

Designing a program by discovering objects, their properties, and their relationships.

Parameter

An item of information specified to a method when the method is called.

Private

The access specifier that determines a feature is accessible only by the methods of the same class.

Public

The access specifier that determines a feature is accessible by all classes.

Public interface

The features (methods, fields, and nested types) of a class that are accessible to all clients.

Return

The keyword that returns a value from a method, with the data type matching the return type in the method heading.

Return type

The value returned by a method through a return statement, specified in the method heading.

State

The current values of the attributes of one instance of an object.

This

The keyword that references the instance of the Object currently being processed.

Type

A named set of values and the operations that can be carried out with them.

Visibility

The access specifier indicating who can see a method or data.

@param

A javadoc keyword used to define a single formal parameter in a javadoc comment.

@return

A javadoc keyword used to define the information being returned by a method in a javadoc comment.

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