Lecture 8, CS 302-6, September 21

1. Review
1. Strings
2. Decisions

i. Tree structure

3. Comparisons
4. From end of last class:

i. Substring of end, beg index, eg substring(3,1)

ii. Ifs without elses are ok

1. We’ll show an example of this eventually

2. Decisions
1. If/Else
2. Else If
3. Nested branches

i. Example – Birthday.java

3. Switch statement
1. Another way for writing long chains of if elses
2. Only ints/chars allowed as input to switch()

i. (actually, in Java 7, String is allowed as well)

3. Only = = operador is used by case. >, !=, etc not supported
4. Structure:

switch (digit)

{

//Execute case 1 if digit==1

case 1: do something; break;

//do case 2 if digit==2

case 2 : do something else; break;

//If digit !=1 and digit !=2 do this

default: do the default behavior; break;

}

4. Booleans
1. For storing whether a logical condition is true or false.
2. 1==1? True! 1+1==1? False!
3. Possible values: true, false

boolean bool=true;

boolean bool2=(1==1); //true

boolean bool3=false;

boolean bool4=(1+1==1); //false

4. Use in conditions:

i. if(bool)…

5. Boolean operators
1. Boolean operators allow us to program more logic into our conditions

i. && -> And

ii. || -> Or

iii. ! -> Not

2. Boolean truth tables

i. A&&B, A ||B, !A

3. Order: !, then &&, then ||

i. A || B && !C means A || (B && (!C))

ii. Rule of thumb: When in doubt, use ()

4. Note – exams will have precedence table
5. Implicit Booleans: if(1==2 || 3>2) etc

i. 1==2 and 3>2 can both be interpreted as booleans

6. HW
1. R3.7, R3.8, R3.19
2. P3.9, P3.24