Fields and Classes

Computer capabilities

• sequence
• store and retrieve
• modify sequence
• i/o
• arithmetic
• comparison

Tracing

• We need to know how to trace programs
• Execute mentally and/or on paper

Trace AccountTester

    public class AccountTester
    psv main
    Account a
    a = new Account(10000.0)

Now lets implement class Account

• Constructor with param
  • initialize private field balance
• Constructor without param
  • initialize to 0
• getBalance
• Deposit: with local
• Withdraw

Three kinds of variables

• local
• parameter

• field

• differ in scope

Variable scope

• Set of statements over which a variable is visible
• local: From point of def to closing }
• parameter: entire method
• field: entire class

Using this

• Within the class we can say `this.balance`