CS200 Computer Science I
Kevin Sahr, PhD
Lecture 14
Menu Application
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Menus
✴common application approach: allow the
user to choose what to do via a menu
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Pseudocode
✴an algorithm for a Menu:
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do it again = true
while do it again
input menu choice
process menu choice
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Loop Condition
✴can often simplify the logic of a loop by using a
boolean variable for the condition
boolean again;
again = true;
while (again)
{
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set again to false if QUIT chosen
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} // while
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Pseudocode
✴an algorithm for a Menu:
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do it again = true
while do it again
input menu choice
process menu choice
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Processing Pseudocode
✴algorithm Process Menu Choice:
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if first choice chosen
do first choice action
else if second choice chosen
do second choice action
... etc. ...
else if quit chosen
do it again = false
else
output “invalid choice”
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Menu Example
✴EX: have the user input a real number and
then use a menu to let the user choose to
square the number, take its inverse, or quit
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Pseudocode
✴pseudocode for our solution:
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input x
build menu prompt string
do it again = true
while do it again
input menu choice
process menu choice
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Input the Number
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double x;
x = Input.readDouble("Enter the number: ");
✴could echo the input value now, but slicker to
include the value in our menu prompt
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Pseudocode
✴pseudocode for our solution:
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input x
build menu prompt string
do it again = true
while do it again
input menu choice
process menu choice
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10
Menu Prompt
✴build our menu prompt string
String menu;
menu = "Choose what to do with " +
x + ":\n";
menu = menu + "a. Square it.\n";
menu = menu + "b. Take its inverse.\n";
menu = menu + "c. QUIT.";
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Pseudocode
✴pseudocode for our solution:
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✴
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✴
input x
build menu prompt string
do it again = true
while do it again
input menu choice
process menu choice
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Input Menu Choice
✴use readChar (or readInt as appropriate) to let
the user choose from the menu
✴use the menu prompt String we built earlier
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choice = Input.readChar(menu);
Output.showValue("You chose: ", choice);
• displays the menu prompt
string
• returns the user’s choice
• we will validate the choice
in the next step
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Pseudocode
✴pseudocode for our solution:
✴
✴
✴
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✴
✴
input x
build menu prompt string
do it again = true
while do it again
input menu choice
process menu choice
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14
Choice Pseudocode
✴processing a menu choice pseudocode:
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if first choice chosen
output x squared
else if second choice chosen
output inverse of x
else if quit chosen
do it again = false
else
output “invalid choice”
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Source Code
✴see Menu.java for complete Java
application
✴spend some time looking at and
experimenting with Menu.java
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Module 14 Vocabulary
no new vocabulary
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