Complete Program

Translating the polynomial 7x³- 3x² + 4x - 12 into Java is easy. The term x³ means x times itself three times, so that is what the Java statement does.

The next statement, that writes out the answer uses "+" to concatenate Strings. Remember that doubles are converted to Strings automatically when you use "+" with both a double and a String.

import java.io.*;

class evalPoly
{
  public static void main (String[] args ) throws IOException
  {
    BufferedReader userin = 
        new BufferedReader(new InputStreamReader(System.in) );

    String xChars;                 // character version of x, from the user    
    double x;                      // a value to use with the polynomial
    double result;                 // result of evaluating the polynomial at x
    String response = "y";         // "y" or "n"

    while ( response.equals( "y" ) )    
    {
       // Get a value for x.
       System.out.println("Enter a value for x:")  ;
       xChars = userin.readLine()  ;
       x   = ( Double.valueOf( xChars ) ).doubleValue();

       // Evaluate the polynomial.
       result =7*x*x*x - 3*x*x + 4*x - 12;

       // Print out the result.
       System.out.println("The value of the polynomial at x = " +
           x + " is :" + result + "\n" ) ;

       // Ask the user if the program should continue.
       System.out.println("continue (y or n)?");

       response = userin.readLine();      
    }

  }
}