Designing Classes

Designing Classes

1. Encapsulation: Allows for a programmer to hide a variable hidden using the private field. To get the value, the programmer can create an accessor method

2. Cohesion/Coupling

   • Cohesion: All interface features are closely related to the single concept that the class represents.
   • Coupling: When many classes of a program depend on each other. It is important to keep a check to make sure that coupling is not too low or too high.

3. Variables

   • Instance variables: variables that are private to the class, requires an accessor method to get it.
   • Variable scope: It is the scope of where and how much a variable can be accessed from. You want to minimize who gets access by thinking about who would really need it.
   • Static variables: Used to set the variable a certain value that is set throughout the whole class. You use the static field.

4. Methods

   • Accessor: Returns a value
   • Mutator: changes the program.
   • Immutable objects: objects that are not able to be changed.
   • Side effect: This is anything that modifies another object, this includes console outputs.
   • Pre-conditions: parameters.
   • Post-conditions: things that the method returns/modifies.
   • Constructor: sets the values to the instance variables and takes in parameters. It is called as soon as you use the class to make an object.
   • Passing parameters
     • Implicit parameter: name of the object or class
     • Explicit parameter: values you are giving to the method.

5. Accessor Modifiers: Both return a value and also mutate the program.

6. Packages: A set of related classes. For example, the java library consists of several hundred packages.