Loops in Java

1
Loops in Java

• For loop
• Do loop
• While loop

2
Boolean Operators

• Comparison Operators
• lt
• lt
• gt
• gt
• !
• Binary Operators
• and
• or
• not !

3
Simple Control Structures

• To alter sequential execution we need control
  structures
• means to test and evaluate
• conditionals
• means to repeat and iterate
• loops

4
Need for Iteration

• Loops are needed to avoid repetitive code
• Conditionals execute only once!

5
While loop

• boolean test for entry (loop guard)
• body of the loop
• may not execute at all
• x 5
• while(x lt 100 x gt 0)
• g.drawOval(x,y,15,15)
• x x 50

6
For Loop

• initialization
• loop guard
• update
• body of the loop
• may not execute at all
• for(x 5 x gt 0 x lt 100 x x 50)
• g.drawOval(x,y,15,15)

7
Do loop

• boolean test for exit
• body of the loop
• always executes at least once
• x 5
• do
• g.drawOval(x,y,15,15)
• x x 50
• while(x lt 100 x gt 0)

8
Designing a Loop

• When do we stop?
• Reverse (or negate) the stopping condition
• loop guard
• What is the initial state?
• Update the appropriate variables
• infinite loop
• What is that needs to be repeated?
• body of the loop

9
Homework

• Read the following
• Chapter 8 (BP)
• Lab 04 is due this coming Sunday the 25th
• Go over Exercise_7.doc
• Exam I is on Thursday the 29th
• Open book open notes
• 2 problems similar to labs 3 4
• 70 minutes