CS141: Topics for Sept 9, 11 & 13, 2013

Homework and Reading

The reading and homework for this week can be found here: Lab 3: Decisions

Chapter 3 Vocabulary

• Medical example
  • Pseudo code - What to do if you have a fever or not.
• If-statement, if-else –
  • Syntax
  • Braces & indentation
  • Boolean values and variables:
    • What is a boolean variable? (boolean, true/false)
    • Relational operators – making number comparisons with <, >, <=. >=, ==, !=
    • Be careful!! Equality of Strings. Do not use ==. Instead, use myString1.equals(myString2)
• Adding Complexity: Multi-way, nested if-else
  • Branch, branching, flow charts
• Boolean operators &&, ||, ! Watch precedence. Write out truth tables.
  • Combining with relational operators
• Strings and lexicographic ordering – compareTo operator
• Rules of Thumb & Common Errors:
  • Avoid duplication in branches
  • Dangling else problem
  • Syntax for condition ( 5 < x < 7 ) is NOT allowed! Need to use boolean operators.
• De Morgan's Law:
  • !(A && B) same as (!A) || (!B)
  • !(A || B) same as (!A) && (!B)
• Input validation (will work better after we do loops in chapter 4)
• Less Commonly used structures (not recommended at the moment):
  • Conditional Operator :
    • condition ? value1 : value2;
    • Example: int bigger = (x>y) ? x : y ;
  • Switch statement: switch (digit) { case a: break; ...default: ... }
    where digit can be byte, short, int, char, enumerated types, and (recently) Strings
  • Enumeration Types, e.g. see example
• Random numbers and picking cards.

In Class Practice Activities

• In the beginning of class. Redo the loan payment from from before. Try not to look at the program you did before unless you get really stuck.
  • Start with a brand new Netbeans Project.
  • Create a Java class file called LoanPaymentApp.java.
  • Remember that you need to declare and initialize 4 variables: loan amount, yearly interest rate percentage, the length of loan in years, and the monthly payment (calculated by you).
  • You then need to calculate the monthly interest rate in decimal (not percent) and the length of loan in months (not years).
  • The formula for the payment can be found at this website.
  • Print the result out.
  • Clean up your code: fix the formating and add comments including your name and date at the top.
  
  When you are done, you may compare it with the version here: LoanPaymentApp.java
• See instructions for the medical diagnosis system: Doctor, Doctor!

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