Chapter 8: Designing Classes

Preconditions and Postconditions

• Precondition: amount >= 0
• assert amount >= 0; // assertions must be enabled
• Postcondition: getBalance() >= 0
• assert getBalance() >= 0; // assertions must be enabled
• Some javadoc extensions support @precondition and @postcondition tags

static

• methods, also called class methods, e.g. Math.random();
• variables, also called class variables (or fields), e.g. private static int lastAccount = 1000;

Scope Rules

• The scope of a variable is the region of a program where the variable can be accessed.
• Instance Variables, Instance Methods - can be qualified with this.
• Class Variables, Class Constants, Class Methods - can be qualified with name of class
• Method Parameters
• Local Variables

Lecture Code

We continued to modify and comment the solution to Program 1 to illustrate some of the above concepts.

• TestProgram.java
• GringottsAccount.java