Mathematical Functions in Java

Math is pretty simple in Java, as long as you aren't writing complex equations!

Let's go over the core math operators.

int mySum = 1 + 2; //now equals 3
int myDiff = 2 - 1; // now equals 1
int myMult = 2 * 3; // now equals 6
int myDiv = 6 / 3; // now equals 2

You can also use variable names instead of the actual numbers.

int num1 = 2;
int num2 = 2;
int sum = num1 + num2 + 10; // 2 + 2 + 10 = 14

What about decimals?

int myDiv = 3 / 2 // does it equal 1.5?

No, it equals 1, because the int type only holds whole numbers, do it will disregard the decimal completely.

double myDiv = 3 / 2 // does this work now?

Still no! It would equals 1.0. This statement still divides two integers, so the result will be an integer.

In order to fix this, at least one number in the equation needs to be represented with a decimal. Your answer will now contain the decimal.

double myDiv = 3.0 / 2;
double myDiv = 3 / 2.0;
double myDiv = 3.0 / 2.0;

//These all give the same result - 1.5

What about more complex operations, like square root? Luckily, Java provides built-in functions that will do this for you. You don't have to create the operations yourself!

int squareRoot = Math.sqrt(16); // equals 4

The dot (.) notation that you see above in Math.sqrt(x) is calling a method in the Math class called sqrt(). We'll look at functions and classes indepth soon! For now, just notice the syntax to call a method that is part of a class.

Java has a lot of other built in math operations as well. If it's a common math operation, then Java likely has it.

double myNum = Math.tan(2); //returns the tangent of a number
//sin, cos, atan, etc. also exist!

int bigNum = Math.exp(55); //exponential function

Remember constants from the last lesson? The Math class also contains a few constants.

//Let's find the circumference of a circle
double radius = 2.5;
double circumference= Math.PI * 2 * radius;

Beginner college courses often give assignments that require you to use Math.PI or other constants, so remember that they are here for your convenience!

Of course, you can also use your own constants.

final double savingsAccountInterestRate = 2.2;

double balance = 2000.00;

//calculate balance in one month
double newBalance = balance + (balance * (2.2 / 100)); // equals 2044.00

It's cumbersome to write Math. before every use of the library. We can avoid this by using a static import of the Math class.

import static java.lang.Math.*;

double mySquare = sqrt(25);

We will discuss imports later, so don't worry too much about it for now. Just be aware that you can use this to write less code and achieve the same result.

The basics of math in Java are fairly straightforward and intuitive. We all know that math is a tough subject, but luckily, the syntax is fairly straightforward. Remember: even by practicing simple math problems, you're practicing Java syntax, and you are one step closer to mastery!