Java as a Calculator

All of the familiar mathematical functions that are found on an electronic calculator such as sine, log, and square root are available to your program in the Java Math class. Typically these functions expect data type double as an actual parameter and return a double value.

Here is a program that reads in a floating point number from the keyboard and prints out its square root:

import java.io.*;
class SquareRoot
{
  public static void main (String[] args) throws IOException 
  {
    String charData;
    double value;

    // read in a double
    BufferedReader stdin = new BufferedReader 
        (new InputStreamReader(System.in));
    System.out.print  ("Enter a double:");
    charData = stdin.readLine();
    value  = Double.parseDouble( charData  ) ;
    
    // calculate its square root
    double result = Math.sqrt( value );
    
    // write out the result
    System.out.println("square root: " + result );
  }
}

The assignment statement (in blue) uses the sqrt() method of the class Math. This is a static method, which means that you ask for it using the name of a class and a dot operator, like this:

Class . method ( parameters )