7.3a p 249
expression
7==7
outcome
7.3a p 249
expression
outcome
7==7
true
7.3b p 249
expression
'b'>='A'
outcome
7.3b p 249
expression
outcome
'b'>='A'
true
The Unicode encodings of 'A' and 'b' are
65 and 98.
7.3c p 249
expression
6<8 && 'a'<'b'
outcome
7.3c p 249
expression
outcome
6<8 && 'a'<'b'
true
both 6<8 and 'a'<'b' are true.
7.3d p 249
expression
true!=false || 7>7.5
outcome
7.3d p 249
expression
outcome
true!=false || 7>7.5
true
true!=false is true. The whole condition is true
because of the or.
7.3e p 249
expression
Color.red<3
outcome
7.3e p 249
expression
outcome
Color.red<3
Syntax error
It doesn't make sense to compare a Color
object and an integer.
7.3f p 249
expression
0<3<7
outcome
7.3f p 249
expression
outcome
0<3<7
Syntax error
such an expression is read left to right. 0<3 is
evaluated first and is equal to true. Then true is
compared to 7. But it is a mistake in java to compare
a boolean and an int.
7.3g p 249
expression
"CAT" != null
outcome
7.3g p 249
expression
outcome
"CAT" != null
true
"CAT" is a valid reference to a String object.
7.3h p 249
expression
"Z" == 'Z'
outcome
7.3h p 249
expression
outcome
"Z" == 'Z'
Syntax error
"Z" is a String object. 'Z' is a char, one of the
primitive types of java. It doesn't make sense to
compare an object with a primitive type.
7.3i p 249
expression
"A" == ""+'A'
outcome
7.3i p 249
expression
outcome
"A" == ""+'A'
Can't tell: true/false
""+'A' is the String "A". But here memory locations are
compared. Not the String contents. To compare the
content of 2 Strings, use the method equals:
"A".equals(""+'A') is true.
"A"==""+'A' is true if the compiler optimizes the storage
of Strings and recognizes that "A" and ""+'A' are the
same thing. It is false if not. For instance, "A"==new
String(""+'A') is false, since in that case one creates
explicitly a String for ""+'A'.
7.4c p 249
P
false
false
false
false
true
true
true
true
Q
false
false
true
true
false
false
true
true
R
false
true
false
true
false
true
false
true
!((Q && R) || (P && !R))
7.4c p 249
P
false
false
false
false
true
true
true
true
Q
false
false
true
true
false
false
true
true
R
false
true
false
true
false
true
false
true
!((Q && R) || (P && !R))
true
7.4c p 249
P
false
false
false
false
true
true
true
true
Q
false
false
true
true
false
false
true
true
R
false
true
false
true
false
true
false
true
!((Q && R) || (P && !R))
true
true
7.4c p 249
P
false
false
false
false
true
true
true
true
Q
false
false
true
true
false
false
true
true
R
false
true
false
true
false
true
false
true
!((Q && R) || (P && !R))
true
true
true
7.4c p 249
P
false
false
false
false
true
true
true
true
Q
false
false
true
true
false
false
true
true
R
false
true
false
true
false
true
false
true
!((Q && R) || (P && !R))
true
true
true
false
7.4c p 249
P
false
false
false
false
true
true
true
true
Q
false
false
true
true
false
false
true
true
R
false
true
false
true
false
true
false
true
!((Q && R) || (P && !R))
true
true
true
false
false
7.4c p 249
P
false
false
false
false
true
true
true
true
Q
false
false
true
true
false
false
true
true
R
false
true
false
true
false
true
false
true
!((Q && R) || (P && !R))
true
true
true
false
false
true
7.4c p 249
P
false
false
false
false
true
true
true
true
Q
false
false
true
true
false
false
true
true
R
false
true
false
true
false
true
false
true
!((Q && R) || (P && !R))
true
true
true
false
false
true
false
7.4c p 249
P
false
false
false
false
true
true
true
true
Q
false
false
true
true
false
false
true
true
R
false
true
false
true
false
true
false
true
!((Q && R) || (P && !R))
true
true
true
false
false
true
false
false