Arithmetic
Arithmetic expressions translate mathematical formulas into computer instructions.
Most arithmetic operators take two operands. (We would say they are binary operators.)
- Addition and subtraction of two numbers:
length + 6.13 5 - radius - Multiplication and division of two numbers:
width * height total / 2 - Modulus (remainder) of two numbers:
15 % 4 year % 100
Practice Exercise¶
The modulus, %, gives us the remainder, telling us if the first number is divisible by the second. For example, 13 divided by 5 is 2, leaving a remainder of 3:
* 13 % 5 == 3
* 14 % 5 == 4
* 15 % 5 == 0 : 15 is divisible by 5.
A particularly important use of this is determining if a number is odd or even.
* 3 % 2 == 1 : 3 is odd
* 4 % 2 == 0 : 4 is even
* 5 % 2 == 1 : 5 is odd
* 6 % 2 == 0 : 6 is even
A few operators work with just one operand (unary operators):
- To use the negative of a variable's value, precede it with the
-operator:
-score
+ operator, but using it doesn't do anything.
Many subexpressions can be combined to form a final result:
volume = 4.0 / 3.0 * 3.14159 * radius * radius * radius;
Expressions often have many operators. Each operator is evaluated in turn (left to right), with the result used as an operand for the next operator.
For example, if radius is 2.5, the operands are derived in the order 1-6:
Drill¶
Expressions/src/drills/Arithmetic.java
* Run this program with several numbers. What happens to the remainder when you do integer division?
* Comment out the call to doDivision();
* Uncomment the call to doModulus();
* Complete the method and use the modulus operator to find the remainder.
Expressions/src/drills/MilesPerGallon.java* Complete the code according to the TODO's in comments.