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Lecture 3

IT 1090C Lecture 3: Boolean Variables


Department
Information Technology
Course Code
IT 1090C
Professor
Wulf Tom
Lecture
3

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3.7 Boolean Variables
A Boolean variable is often called a flag because it can be either up (true) or down (false)
Boolean is a Java data type
Boolean failed= true;
Can be either true or false
Boolean Operators: && and I I
They combine multiple conditions
&& is the and
operator
I I is the or
operator
Combining two conditions is often used in range checking
Is a value between two other values?
Both sides of the and
must be true for the result to be true
If only one of two conditions need to be true
Use a compound conditional with an or:
If either is true
The result is true
If you need to invert a boolean variable or comparison, combine conditions.
3.8 Input Validation
Accepting user input is dangerous
Consider the Elevator program:
The user may input an invalid character or value
Must be an integer
Scanner can help
hasNextInt
True if integer
False if not
The range check value
We expect a floor number to be between 1 and 20
Not 0, 13 or greater than 20
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