This document discusses while and do-while loops in Java. It covers the syntax of while and do-while statements and explains the logic and flow of each loop. While loops check the condition before the loop body executes and may execute zero times, while do-while loops check the condition after executing the body so the body always runs at least once. Examples are provided to illustrate infinite loops, nested loops, and how while and do-while statements compare.

1. CSE110
Principles of Programming
with Java
Lecture 11:
Loops: while and do/while statements
Javier Gonzalez-Sanchez
javiergs@asu.edu
javiergs.engineering.asu.edu
Office Hours: By appointment

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Topics
class
global
variables
methods statements
instructions
local
variables
conditional
Statements
if-else
switch
?:
loop
Statement
while
do-while
for

3. while Statement

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The while Statement
• The while statement has the following syntax:

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Logic of a while Loop
zero or more

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Example 1

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The while Statement
• Note that if the condition of a while statement is
false initially, the statement is never executed
• Therefore, the body of a while loop will execute
zero or more times

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Infinite Loops
• The body of a while loop eventually must make the
condition false
• If not, it is an infinite loop, which will execute until
the user interrupts the program
• This is a common logical error

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Example 2

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Nested Loops
• Similar to nested if statements, loops can be nested
as well. That is, the body of a loop can contain
another loop
• Each time through the outer loop, the inner loop
goes through its full set of iterations

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Example 3

12. do-while Statement

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The do-while Statement
• The do-while statement has the following syntax:

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Logic of a do-while Loop
one or more

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Example 4

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The do-while Statement
• A do loop is similar to a while loop, except that the
condition is evaluated after the body of the loop is
executed
• Therefore the body of a do loop will execute at
least once

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Example 5

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Comparing while and do-while

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Test yourselves
?

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Reference
Chapter 4

21. CSE110 - Principles of Programming
Javier Gonzalez-Sanchez
javiergs@asu.edu
Summer 2017
Disclaimer. These slides can only be used as study material for the class CSE110 at ASU. They cannot be distributed or used for another purpose.