1. Some revision

2.  Today, we will do some revision on: - ◦ booleans, and ◦ if statements

3. What is stored in the variable v after this code is run? boolean v = !(20 == 20); What is stored in the variable q after this code is run? int d = 18; int f = 20; boolean q = d == f; What is stored in the variable w after this code is run? int d = 16; int g = 18; boolean w = d != g; false true

4. What is stored in the variable w after this code is run? boolean d = true; boolean h = true; boolean w = d || h; What is stored in the variable w after this code is run? boolean d = true; boolean f = false; boolean w = d && f; false true

5. What is stored in the variable n after this code is run? boolean c = true; boolean h = false; boolean w = true; boolean n = c || h || w; What is stored in the variable x after this code is run? int b = 5; int g = 3; boolean x = (b 8); true TT TF

6. What is stored in the variable r after this code is run? int b = 9; int e = 5; boolean r = (b >= 10) && (e <= 7); What is stored in the variable s after this code is run? int a = 9; int h = 2; boolean s = !(a >= 7) && !(h <= 1); false F T TF

7.  This is the basic structure of an if....else statement in java: if ( condition_to_test ) { then_ clause } else { else_clause } // end if (optional comment)  If the Pseudocode was : - ◦ if “the average mark is over 59” ◦ then the degree classification is 2.1 ◦ else the degree classification is 2.2  What would the code be if average has the value 65?

8. int average = 65; String result; if ( average > 59 ) { result = " 2:1 " ; // then clause } else { result = " 2:2 " ; // else clause } // end if

9. if ( condition_one ) { then_clause } else { if ( condition_two ) { then_clause } else { else_clause } // end inner if } // end outer if   Anything not caught by the first two conditions will be caught by the final else.

10.  Try this out: -  Assume that you can have three grades for a MSc module: ◦ distinction, ◦ pass or ◦ fail.  A distinction is a grade over 70, a pass is a grade over 50, and a fail is everything else.  How would you code this?  Jot down what you think before we look at the answer on the next slide. if ( condition_one ) { then_clause } else { if ( condition_two ) { then_clause } else { else_clause } // end if

11. if ( grade > 70 ) { Result = " Distinction " ; } else { if ( grade > 50 ) { Result = " Pass " ; } else { Result = " Fail " ; } // end if inner outer

12.  Although this would work, any user error could give a result which would seem correct but could cause administrative problems later on.  What kind of errors could cause problems?

13. if (grade > 70 && grade < 101) { Result = " Distinction " ; } etc....  There are many different comparison operators that you can use which cover every combination of events.  Imagine that you wanted to know if a car was either 5 or 6 years old. You would use the OR operator ||.  How would you put this into an if condition?

14. if (carAge == 4 || carAge == 5) { Result = " Buy it " ; } // end if  Note the == sign which is a way of testing if something is equal to for numeric variables.  Remember how to test String variables? String word1 = "Java"; String word2 = "Java"; System.out.println("same = " + word1.equals(word2));

15.  You have various pieces of work to finish for next week.  Ensure that jafa is up to date.  Read Currie (ch 5).  Do the dry run on paper so that you can have a go at the “mock” test in the workshop next week.  Work through the workbook, ensuring that you can understand all of it. If you don’t understand anything, ask in the workshop.