Construct Account class

• [Draw UML diagram]
  • attributes: user (string), pinCode, failedAttempts
  • methods: constructor w/ user, pin;
    getUser, isAuthenticated(user, pin), resetFailures, isAcceptableNewPin, setPin
• Implement constructor, getUser
• implement reset failures to zero
• Implement isAuthenticated:
  • return false if too many failures
  • return true if match user and pin code, reseting # failures
  • increment number of failures otherwise
  • What would happen if increment number of failures when above max?
• Implement isAcceptableNewPin
  • Ensure not same pin and new pin is large enough
  • Convert pin to string of characters, loop through each checking if character matches any remaining ones
    • Use .charAt
• Implement setPin
  • Call isAcceptableNewPin
  • If not acceptable, print error and do System.exit
• Discuss AccountTest.java
• Discuss javadoc and Account.java
• Consider encapsulation
  • what if opponent gets a memory dump?
  • Could encode pinCode, even user
  • Simple encoding: negate and add 53
  • Observe value in trace
  • Show passes tests

Today's Goals

• Define and use class constants
• Understand the importance of information hiding and encapsulation
• Define and use methods that have reference data types as arguments - String values
• Define and use overloaded methods - add method to check just PIN
• Call methods of the same class - isAcceptableNewPin
• Draw and explain memory diagrams that illustrate the instantiation of objects
• Describe the role of the garbage collector - what happens if set username to a gigabyte of data and then change it?
• Compare the equality of two different objects - add method to compare usernames
• Swap the data in two different objects - add method swapPinCodes
• Avoid redundant code by calling one constructor from a different constructor - add constructor with just username, default pinCode to 0

Exam 2 Review

• Java API
  • Math.sqrt, Math.pow, Math.sin/cos/tan, Math.abs, Math.PI
  • Additional types: double, float, int, long, short; approx ranges
  • Wrappers for primitive types: Integer, Float, Double, etc.
  • Double.toString
  • Double.parseDouble, etc.
  • String: length, substring, charAt
• Loops: while, for, do
• more on if, switch
• steps to write a loop
• !(x && y) equivalent to !x || !y
• classes, UML diagram for a class
• attribute, method
• public vs. private
• accessor, mutator methods
• conventions for method names