To square a number you multiply it by itself. For example if you multiply 4 by itself – 4×4 – you are squaring the number 4. Another way to say this is to raise 4 to the power of 2, or 4². is the same as 4×4 which equals 16.

To get the square root of a number you have to think of the square in reverse:

4 squared is 16, so a square root of 16 is 4

Question, what is the 3 squared?

Question: What is the square root of 9?

So, a square root of a number is a value that can be multiplied by itself to give the original number.

As you might expect, Java has a method for this so you don’t need to calculate square roots for your self. This is called the sqrt() method and the general syntax (where x is the number you wish to find the square root of) is:

Math.sqrt(x)

Let’s see how we might use the sqrt() method in Java:

//Output the square root of 9
System.out.println(Math.sqrt(9));
//Output the square root of 16
System.out.println(Math.sqrt(16));
//Output the square root of 25 as an integer
System.out.println((int)Math.sqrt(25));

The output should be 8², 8³ and 8⁴:

run:
3.0
4.0
5
BUILD SUCCESSFUL (total time: 0 seconds)

Note that sqrt() will return a double value, so if you would like to remove the decimal point you can type cast the result to an integer.

Read more about the Math class here: https://docs.oracle.com/javase/8/docs/api/java/lang/Math.html