Sure, boolean variables are nice. Boolean expressions are even better. Below are a couple of examples.
Is one greater than two?
1 > 2
Of course not, so the answer is false.
Is two greater than one?
2 > 1
It is, so it must be true!
Is X greater than two?
x > 2
We can’t answer this until we know the value of x!
int x = 0; boolean isXGTRThan = x > 2; // what's the value of isXGTRThan? x = 2013; isXGTRThan = x > 2// what's the value of isXGTRThan?
There are a number of operators that can be used in Boolean expression:
- greater than: >
- less than: <
- equal to: ==
- greater than or equal to: >=
- less than or equal to: <=
int x = 5; boolean expression = x > 2; x = 3; expression = x < 4; // what's the value of expression? x = x; // what's the value of x? expression = 5 >= x; // what's the value of expression? expression = x == x; // what's the value of x and expression?
We can build even larger Boolean expressions with logical conjunctions and disjunctions.
- The conjunction operator is: &&. This denotes a logical ‘and’.
- The disjunction/disjoint operator is: ||. This denotes a logical ‘or’.
boolean one = true; boolean two = true; boolean three = false; boolean expression = one && two; // what is the value of expression? expression = one || three; // what is the value of expression? expression = one && three; // what is the value of expression?
Let’s see how well you know this stuff. 🙂
boolean expression = ((true && false) || (3 < 2)); // what's the value of expression?