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# Thread: multiplication of polynomials method functionality

1. ## multiplication of polynomials method functionality

Hello i am trying to work out how to multiply two polynomials entered from keyboard input together. Have got the addition working, and multiplying by a constant. But am unable to get the multiplication method and functionality right.
You can see my attempt at multiplication under multiply by a monomial code.

Any help is appreciated.

thanks

```
import java.util.*;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.text.*;
import java.io.IOException;
import java.util.Iterator;
import java.util.Scanner;

public class Polynomial
{
private int TOLERANCE = 0;

/******************  the  Monomial (inner) class   ********************************/

private class Monomial
{
private DecimalFormat precision = new DecimalFormat("#.####");
private int deg;     // degree of polynomial
private int coeff; // coefficients
private Monomial next; // Pointer to next term

public Monomial(int coeff, int deg, Monomial next)
{
this.coeff = coeff;  	//coefficient
this.deg = deg;  		// Degree
this.next = next;		// Pointer
}
public String toString()
{
String form = precision.format(Math.abs(coeff));

if(deg == 0) return form ;
else
if(deg == 1) return form + "x";
else
return form +"x^" + deg;
}
public boolean equals(Monomial mono)
{
return coeff == mono.coeff && deg == mono.deg;
}

}

//*********************************************************************************************

public Polynomial()
{
}

/***************************************************************************
*  Adds a new term into the polynomial, assuming that the polynomial
*  is sorted in order from smallest to largest exponent.
**************************************************************************/
public void addTerm(int coeff, int deg)
{
if( Math.abs(coeff) < TOLERANCE ) return;

{
return;
}

Monomial prev = null;

while( cur != null && deg > cur.deg)
{
prev = cur;
cur = cur.next;
}
if( cur == null || deg != cur.deg )
prev.next = new Monomial(coeff, deg, cur);
else
{
cur.coeff += coeff;
if( Math.abs(cur.coeff) < TOLERANCE )
if(prev != null)
prev.next = cur.next;
else
}
}

public String toString()
{
StringBuffer sb = new StringBuffer();

for(Monomial tmp = head; tmp != null; tmp = tmp.next)
if(tmp.coeff < 0 )
sb.append(" - " + tmp.toString());
else
sb.append(" + " + tmp.toString());

return sb.toString();
}

//*********************************************************************************************

/*********************************************************************************************

*  Return the degree of this polynomial

**********************************************************************************************/

//*********************************************************************************************/

/*********************************************************************************************
*  Multiplies Polynomial 1 to Polynomial 2
*  The method does not change the original polynomial.
**********************************************************************************************/

//*********************************************************************************************/

/*********************************************************************************************
*  Adds Polynomial 1 to Polynomial 2
*  The method does not change the original polynomial.
**********************************************************************************************/
{
Polynomial res = clone();

for(Monomial tmp = poly.head; tmp != null; tmp = tmp.next)

return res;
}

public Polynomial clone()
{
Polynomial res = new Polynomial();

for(Monomial tmp = head; tmp != null; tmp = tmp.next)

return res;
}

public boolean equals(Polynomial poly)
{

while(tmp1 != null && tmp2 != null)
{
if( !tmp1.equals(tmp2) ) return false;
tmp1 = tmp1.next;
tmp2 = tmp2.next;
}
return true;
}

//*********************************************************************************************/

/*********************************************************************************************
*  Multiplies by a Constant
*  The method does not change the original polynomial.
**********************************************************************************************/

public Polynomial multiply(int num)
{
Polynomial res = clone();

for(Monomial tmp = res.head; tmp != null; tmp = tmp.next)
tmp.coeff *= num;

return res;
}

//*********************************************************************************************/

/*********************************************************************************************
*  Returns a new polynomial that is the derivative of this polynomial.
**********************************************************************************************/
public Polynomial diff()
{
Polynomial res = new Polynomial();

for(Monomial tmp = head; tmp != null; tmp = tmp.next)
{
if(tmp.deg != 0)
res.addTerm(tmp.coeff * tmp.deg, tmp.deg - 1 );
}

return res;
}

//*********************************************************************************************/

/*********************************************************************************************
*  Returns a new polynomial that is the result of Monomial times polynomial.
**  The method does not change the original polynomial.
**********************************************************************************************/
/*
public Polynomial times(Polynomial poly)
{
{
Polynomial result = new Polynomial();

for(Monomial tmp2 = poly.head; tmp2 != null; tmp2 = tmp2.next)

for(Monomial tmp = head; tmp != null; tmp = tmp.next)

while(tmp != null && tmp2 != null)
{
result.addTerm(tmp.coeff * tmp2.coeff, tmp.deg + tmp2.deg);
tmp = tmp.next;
tmp2 = tmp2.next;
}
return result;

}

}
*/

//*********************************************************************************************/

/*********************************************************************************************
*  Driver Program to Test Polynomial Class
**********************************************************************************************/

public static void main(String[] args)

{

//---------------- Code to chose between keyboard input or file input------------------------

System.out.println("If you would like you enter the polynomial via a text file 'Polyinput.txt' PRESS

1. ");
System.out.println("If you would like you enter the polynomial via the keyboard, PRESS ANY OTHER

INTEGER... ");
Scanner inputquestion=new Scanner(System.in);
System.out.print("Enter Option: "); // Prompts for selection choice
int option=inputquestion.nextInt(); // Stores input in option

if (option == 1) // if loop to jump into read from text file
{

String content = new String();
String name = new String();
File file = new File("polyinput.txt");

try {
Scanner sc = new Scanner(new FileInputStream(file));
while (sc.hasNext()) {
name = sc.next();
content = sc.nextLine();

}

sc.close();
} catch (FileNotFoundException fnfe) {
fnfe.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
System.out.println("\nProgram terminated Safely...");
}

Iterator<String> i = list.iterator();
while (i.hasNext()) {
System.out.println(name + i.next() + "\n");

}

} //------------ End if to enter input text file code---------------------------------------

else  //--------------start of else for keyboard input--------------------------------------
{

//------- Code to Prompt for Polynomial 1

-----------------------------------------------------------------

Polynomial polynomial1 = new Polynomial();
System.out.println( );
System.out.println( );
System.out.println("Enter first Polynomial");
System.out.println("(Enter Zero (0) as Exponent value to move to second Polynomial");
System.out.println( );

//Insert do while loop exponent not equal 0
int ExponentTest = 1;
do {

Scanner inputCoefficent=new Scanner(System.in);
System.out.print("Enter Coefficient: "); // Prompts for coefficent
int Coefficient=inputCoefficent.nextInt(); // Stores coefficent in coefficent
Scanner inputExponent=new Scanner(System.in);
System.out.print("Enter Exponent: "); // Prompts for Exponent
int Exponent=inputExponent.nextInt(); // Stores Exponent in Exponent

if (Exponent < 1)
{
ExponentTest = 0;
}

} while (ExponentTest > 0);
// ------ end do while loop ---------------

System.out.println( );
System.out.println( " Entered Polynomial is: " + polynomial1 );

//----------------------------------------------------------------------------------------------------------

//----------- Code to Prompt for Polynomial 2 -----------------------------------------------------------------

Polynomial polynomial2 = new Polynomial();
System.out.println( );
System.out.println( );
System.out.println("Enter second Polynomial");
System.out.println("(Enter Zero (0) as Exponent value to complete Polynomial");
System.out.println( );

//Insert do while loop exponent not equal 0
int ExponentTest2 = 1;
do {

Scanner inputCoefficent=new Scanner(System.in);
System.out.print("Enter Coefficient: "); // Prompts for coefficent
int Coefficient=inputCoefficent.nextInt(); // Stores coefficent in coefficent
Scanner inputExponent=new Scanner(System.in);
System.out.print("Enter Exponent: "); // Prompts for Exponent
int Exponent=inputExponent.nextInt(); // Stores Exponent in Exponent

if (Exponent < 1)
{
ExponentTest2 = 0;
}

} while (ExponentTest2 > 0);
// ------ end do while loop ---------------

System.out.println( );
System.out.println( " Entered Polynomial is: " + polynomial2 );

//----------------------------------------------------------------------------------------------------------

//------- Code to Prompt for Monomial (ax^k) to multiply both Polynomials by---------------------------------

Polynomial monomial1 = new Polynomial();
System.out.println( );
System.out.println( );
System.out.println("Enter details for the Monomial equation");
Scanner inputMonomial=new Scanner(System.in);
System.out.print("Enter Coefficent: "); //Prompts for Coefficient
int num1=inputMonomial.nextInt(); // Stores Coefficient in num1
System.out.print("Enter Exponent: "); // Prompts for Exponent
int num2=inputMonomial.nextInt(); //Stores Exponenent in num2
monomial1.addTerm(num1, num2); // Creates the Monomial equation

System.out.println();
System.out.println( "Monomial: " );
System.out.println( monomial1 );
System.out.println( );

//----------------------------------------------------------------------------------------------------

//------- Code to Prompt for constant to multiply by and then reads in the constant and stores in Constant1

System.out.println("Enter integer to be used as the constant");
Scanner inputConstant=new Scanner(System.in);
System.out.print("Enter Constant: "); // Prompts for constant
int Constant1=inputConstant.nextInt(); // Stores Constant in Constant1

System.out.println( "Constant used to multiply polynomials: " );
System.out.println( Constant1 );
System.out.println( );

//----------------------------------------------------------------------------------------------------------

//------------------------ Returns display for operations onto the screen-----------------------------------

System.out.println( );
System.out.println( "Degree of Polynomial 1 ("+ polynomial1 + "): " /*+ polynomial1.degree()*/);

System.out.println( );
System.out.println( "Degree of Polynomial 2 ("+ polynomial2 + "): " );

System.out.println( );
System.out.println( "Multiply Polynomial 1 ("+ polynomial1 + ") by Polynomial 2 ("+ polynomial2 + "): " );

System.out.println( );
System.out.println( "Multiply Polynomial 1 ("+ polynomial1 + ") by Monomial ("+ monomial1 + "): " );
System.out.println( monomial1 + " * " + polynomial1 + " = " + MultiplyMonomialResult1 );
System.out.println( );

System.out.println( );
System.out.println( "Multiply Polynomial 2 ("+ polynomial2 + ") by Monomial ("+ monomial1 + "): " );
System.out.println( monomial1 + " * " + polynomial2 + " = " + MultiplyMonomialResult2 );
System.out.println( );

System.out.println( );
System.out.println( "Polynomial 1 (" + polynomial1 + ") plus Polynomial 2 (" + polynomial2 + "): " );
System.out.println( polynomial1 );
System.out.println( polynomial2 );
System.out.println( "=" );
System.out.println( );

System.out.println( "multiply Polynomial 1 ("+ polynomial1 + ") by constant entered into console (ie " +

Constant1 + "): " );
Polynomial MultiplyConstant1 = polynomial1.multiply(Constant1);
System.out.println( Constant1 + " * " + polynomial1 + " = " + MultiplyConstant1 );
System.out.println( );

System.out.println( "multiply Polynomial 2 ("+ polynomial2 + ") by constant entered into console (ie " +

Constant1 + "): " );
Polynomial MultiplyConstant2 = polynomial2.multiply(Constant1);
System.out.println( Constant1 + " * " + polynomial2 + " = " + MultiplyConstant2 );
System.out.println( );

System.out.println( "Derivative of Polynomial 1: " );
Polynomial diffresult1 = polynomial1.diff();
System.out.println( "Polynomial 1: " + polynomial1 );
System.out.println( "Derivative =  " + diffresult1 );
System.out.println( );

System.out.println( "Derivative of Polynomial 2" );
Polynomial diffresult2 = polynomial2.diff();
System.out.println( "Polynomial 2: " + polynomial2 );
System.out.println( "Derivative =  " + diffresult2 );
System.out.println( );

//-------------------------------End Screen output of operations for keyboard entry-------------------------

} // End of else for keyboard input.------------------------------------------------------------------------

}
}```

2. ## Re: multiplication of polynomials method functionality

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