1. Announcements & Review
Last Time:
More on input: Scanner class
While loops
Today
more on While
Methods in a class
Declarations
Parameters
Announcements
Lab 2 Due Thursday 10pm
1 file per pair
Lecture 8: Simple Methods

2. Lecture 8: Simple Methods
When do we while?
boolean condition = true;
// keep doing the loop while condition==true
while (condition) { ….
// somewhere in the loop the condition
// becomes false. Why?
if (test) {
condition = false; }
Lecture 8: Simple Methods

3. Reading Input Features
String word1 = stdin.next();
int number1 = stdin.nextInt();
double dnum1 = stdin.nextDouble();
boolean progress1 = stdin.nextBoolean();
// peeking to make sure the format is right
boolean isString = stdin.hasNext();
boolean isInt = stdin.hasNextInt();
boolean isDouble = stdin.hasNextDouble();
boolean isBoolean = stdin.hasNextBoolean();
Lecture 8: Simple Methods

4. Lecture 8: Simple Methods
BlueJ Examples
Lecture 8: Simple Methods

5. Why Methods? Algorithmic Thinking…
Divide the program up in logical parts
Analogs
book with chapters; recipes; laundry
Laundry
Every Sunday
collect dirty clothes
sort into color piles (& a really dirty pile!)
wash each pile
dry each pile
fold each pile & sort by person
put them up
Lecture 8: Simple Methods

6. Why Methods? Algorithmic Thinking…
Distinct logical function organization
gather, sort, wash, dry, fold, sort, put up
Reuse - repetition
… every week
Parameterize - things that change
sort differs every week
number of piles, drawers, etc.
Lecture 8: Simple Methods

7. Lecture 8: Simple Methods
Reuse
// public - any code can use this class
// class - defines a type of object, Shapes
public class Shapes {
// instance variables - persistent class state
// ...more on this later…
/**
* Constructor for objects of class Shapes */
public Shapes() {
// initialize instance variables }
Lecture 8: Simple Methods

8. Lecture 8: Simple Methods
Reuse
public class Shapes {
// methods in this class - logical, reusable &
// parameterized units
// this method: its name is printBox
// public - any code with a Shape object can call
// printBox on object, e.g., object.printBox
// private - only other Shape methods can call it
// void - returns nothing
public void printBox() { … }
Lecture 8: Simple Methods

9. Lecture 8: Simple Methods
BlueJ Examples
Lecture 8: Simple Methods

10. Lecture 8: Simple Methods
More Questions?
Lecture 8: Simple Methods