java中的ArrayLists和方法

Question

还有，我要做的方法之一是列表中术语的乘积。我应该如何得到所有的系数和指数，并相互乘？

package assignment9;

import java.util.ArrayList;



/**
 * A class to implement a Polynomial as a list of terms, where each term     has
 * an integer coefficient and a nonnegative integer exponent
* @author your name
*/
public class Polynomial
{
// instance variable declarations go here

private int coeff;
private int expo;
ArrayList <String> poly = new ArrayList <String>();

/**
* Creates a new Polynomial object with no terms
*/
public Polynomial()
{
   this.coeff = coeff;
   this.expo = expo;
   this.poly = poly;

  // TO DO: Write constructor body here
}

/**
 * Inserts a new term into its proper place in a Polynomial
 * @param coeff the coeffiecent of the new term
 * @param expo the exponent of the new term
 */
public void insert(int coeff, int expo)
{

    if(expo == 0)
   {
     poly.add(coeff + " ");
   }
   if(expo == 1)
   {
   poly.add(coeff + "x");
   }
   else
   poly.add(coeff+ "x^"+ expo);
}

/**
 * Deletes the first occurrence of a specified term from a Polynomial, or
 * prints an appropriate message if the term does not appear in the 
 * Polynomial
 * @param coeff the coeffiecent of the term to be deleted
 * @param expo the exponent of the term to be deleted
 */
public void delete (int coeff, int expo)
{
   if (coeff != 0)
       poly.remove(coeff);
   else
       System.out.println("The coefficient you are looking for does not  exist");


  // TO DO: write method body here.  The following statement is included
  // only for development purposes.  Remove after implementing the  method 
  System.out.println("delete method called for " + coeff + " " + expo) ;
}

/**
 * Returns the product of all the terms of a Polynomial, as a String
 * E.g. for the polynomial 3x^2 + 7x^3 + 2x^5, will return 42x^10
 * @return the polynomial product, as a String
 */
public String product()
{

  // TO DO: write method body here.  The following statements are included
  // only for development purposes.  Remove after implementing the method
  System.out.println("product method called") ;
  return "product method is under construction" ;
}

/**
 * Returns a polynomial as a String in this form: 3x^2 + 7x^3 + 2x^5
 * @return the polynomial as a String
 */
public String toString()
{
  // TO DO: write method body here.  The following statements are included
  // only for development purposes.  Remove after implementing the method
  System.out.println("toString method called") ;
  return "toString method is under construction" ;
}

/**
 * Reverses the order of the terms of a Polynomial.
 * E.g. the polynomial 3x^2 + 7x^3 + 2x^5 would be 2x^5 + 7x^3 + 3x^2 after
 * reversal
 */
public void reverse()
{
  // TO DO: write method body here.  The following statement is included
  // only for development purposes.  Remove after implementing the method
  System.out.println("reverse method called") ;
}
}

Answer 1

构造函数需要参数：

public Polynomial(int coeff, int expo, ArrayList<String> poly)
{
    this.coeff = coeff;
    this.expo = expo;
    this.poly = poly;
}

然后，通过在构造函数调用中传递参数来创建多项式对象：

Polynomial myPolynomial = new Polynomial (someCoefficient, someExponent, someStringArray);

其思想是，this.coeff=coeff；行执行以下操作：