Conditions in Java
Conditions in Java
Java conditions are Boolean expressions.
…and they can also express more complex ideas
They can often be quite simple:
– true
boolean literals
– false
– age == 4
– x < 6
– height != width
– name.equals("Ahmed")
– keyboard.nextBoolean()
– a variable of type boolean
Boolean expressions can be combined using
logical operators
&& - and
|| - or
! - not
For example:
– age == 4 || weight >= 40
– width == 32 && !(height < 46)
COSC 117 Spring 2014
COSC 117 Spring 2014
1
Truth Tables
A
F
T
A
F
F
T
T
!A
T
F
B
F
T
F
T
A && B
F
F
F
T
A
F
F
T
T
B
F
T
F
T
2
Truth Tables
A
F
T
A || B
??
??
??
??
COSC 117 Spring 2014
A
F
F
T
T
!A
T
F
B
F
T
F
T
A
F
F
T
T
A && B
F
F
F
T
B
F
T
F
T
A || B
F
T
T
T
COSC 117 Spring 2014
3
Truth Tables
4
Operator Precedence
What do we mean by:
A
0
1
A
0
0
1
1
A || B && C
!A
1
0
B
0
1
0
1
A && B
0
0
0
1
A
0
0
1
1
B
0
1
0
T
COSC 117 Spring 2014
A || B
0
1
1
1
A
T
T
T
T
F
F
F
F
5
B
T
T
F
F
T
T
F
F
C
T
F
T
F
T
F
T
F
(A || B) && C
T
F
T
F
T
F
F
F
?
A
T
T
T
T
F
F
F
F
B
T
T
F
F
T
T
F
F
COSC 117 Spring 2014
C
T
F
T
F
T
F
T
F
A || (B && C)
T
T
T
T
T
F
F
F
6
Operator Precedence
Operator Precedence
What do we mean by:
!
&&
||
A || B && C
A
T
T
T
T
F
F
F
F
B
T
T
F
F
T
T
F
F
C
T
F
T
F
T
F
T
F
(A || B) && C
T
F
T
F
T
F
F
F
A
T
T
T
T
F
F
F
F
B
T
T
F
F
T
T
F
F
COSC 117 Spring 2014
C
T
F
T
F
T
F
T
F
A || (B && C)
T
T
T
T
T
F
F
F
Highest
Lowest
For
A || B && C
! A && B
A || ! C && B
7
Example:
 A || (B && C)
 (! A) && B
 A || ((! C) && B)
COSC 117 Spring 2014
8