Loops

New Terminology

pre-condition loop

A loop where the decision to continue occurs before the body of the loop is executed.

post-condition loop

A loop where the decision to continue occurs after the body of the loop is executed.

counted loop

A specific type of precondition loop which includes the initialization, condition, and update in the loop header structure

loop control variable(s)

One or more variables whose value(s) determine how long the loop will continue.

sentinel (sentinel value)

A value which is used to stop (or continue) loop execution.

flag

A boolean value that flags the end condition of a loop execution

accumulator

A variable that serves to accumulate a series of values.  Usually used in summation, but may be used for any repeated operation.

initialization

For loops, this is the place where we set-up one or more variables that will be used to control loop execution.

decision

For loops, this determines how long the loop will continue to execute.

update

For loops, this step changes the loop control variables to approach the ending condition.

body

For loops, this is the code that may repeatedly execute.

Java Specific Terms

while loop

A precondition loop in java

do while loop

A post condition loop in java

for loop

A precondition, counting loop in java

increment operator (++)

decrement operator (--)

Unary operation that adds or subtracts one from the operand. (Ex: counter++;). May be prefix or postfix, but convention is postfix. Do not use except as a statement by themselves.

Class notes

1. Review  lab (Student.java and Grades.java)
2. PA2 - Choices - which of these choices are the best.  Rank order?
1. Do the entire pa correctly
2. Do the entire pa half way (errors, typos)
3. Do part of the pa correctly
4. Do the entire pa but turn it in late
3. Introduce the concept of loops
   • Looping is all about doing an action or a series of actions multiple times

     - see example problem, Loop0.java and Loop1.java

     - must decide on the actions to repeat, the body of the loop

     - Determine body by looking at the end of the loop, not the beginning.

     - must decide how to determine the number of iterations

   • Example count.java
4. Why do we care?
   • Magic 8-ball - Might want to ask multiple times.
   • Most real-world applications will involve looping
   • We can also begin to do error checking in a more interactive way.
5. Types of loops Slides

   - pre-condition (while) - LoopWhile.java

   - post-condition - LoopDo.java

   - counted - LoopFor.java

   Most loops include:

   - setup or initialization

   - decision

   - body of actions

   - update

6. Book examples of loops (referenced in slides)

   - WhileLoop.java

   - TestAverage1.java

   - Squares.java

   - UserSquares.java

   - TotalSales.java