Iteration

1
Iteration

• Robert Stumpf, Professor
• Computer Information Systems
• California State Polytechnic University Pomona

2
Iteration

• Bohm and Jacopini
• Iteration
• Forms
• while loop
• for loop
• do while loop

3
Bohm and Jacopini

• Bohm and Jacopini stated that a Structured
  program contains three constructs
• 1. Sequence
• 2. Selection
• 3. Iteration
• They proved this mathematically

4
Bohm and Jacopini

• This time we are interested in the third
  construct
• It is called iteration which means do again
• Its basic form is the while loop
• The other forms are convenient but can be
  simulated if not present

5
Iteration

• Iteration means to repeat the process
• A while loop has the test at the beginning
• Question resulting in a boolean response
• Process to be repeated
• If question is true, repeat, if false exit loop

6
Iteration

• A do while loop has the test at the end
• do
• Process to be repeated
• Question resulting in a boolean response
• If question is true, repeat, if false exit loop

7
Forms

• Basic While (without a block) int count 0
  while ( count lt 3 )
• System.out.println(count )
• Not using a block is not very useful as only one
  statement is permitted

8
Forms

• Basic While (with a block) int count 0
  while ( count lt 3 )
• System.out.println(count)
• count
• Using a block is better
• The question is asked at the beginning

9
Forms

• Using count Is same as count count
  1
• count -- is also legal
• Its precedence is at the first level along with !
  and (unary)

10
Forms

• Basic For (without a block) for (int i0 i lt
  3 i )
• System.out.println(count)
• The question still is asked at the beginning

11
Forms

• Basic For (with a block) for (int i0 i lt 3
  i )
• System.out.println(count)
• Using a block is better why?

12
Forms

• Do While
• char responsedo
• // code to input, process, and output is here
  response JOptionPane.showInputDialog
  (Enter N if done Y if you wish to do it again
  )
• while (response.charAt(0) Y)
• Question is asked at the end

13
Summary

• Java allows one to iterate three ways
• while loop test at the beginning
• for loop test at the beginning
• do while loop test at the end
• The for loop is for convenience as there are many
  situations requiring one to count

14
Thank You

• Java has Built in Constructs to facilitate
  Iteration
• Any questions should be directed to Professor
  Robert Stumpf
• Email rvstumpf_at_csupomona.edu
• Web Sitehttp//www.csupomona.edu/rvstumpf