Problems with the output of an array

Question

Hallo,
I have got problems with giving out an array.
I declared two arrays and puted them out, but with the
resultarray it doesn�t work. Cansomebody help me?
Here is a runtime output:
Grad eingeben!
1
Koeffizienten eingeben!
1
2
1x^0 + 2x^1 +
1
Grad eingeben!
3
Koeffizienten eingeben!
2
3
4
5
2x^0 + 3x^1 + 4x^2 + 5x^3 +
3
p:1
this:3
And here is the source code
// Die Klasse Polynom dient dem Umgang mit dem Polynom
//Sie enth�llt die Methoden:
//   > public void readCoeffizients()
//   > public void show()
//   > public int getGrad()
//   > public Polynom add(Polynom p)
//Und den Konstruktor:
//   > public Polynom(int  n)
public class Polynom
  private int grad;
  int [] coeffizient;
  private Polynom q1;
  public Polynom(int  n) //Konstruktor mit Stanard-Initialisierung
    this.grad = -1;
    this.coeffizient = new  int [n+1];
    for(int i=1; i<(n+1); i++)
      this.coeffizient[i] = 0;
  public void readCoeffizients() // Methode zum Einlesen der Koeffizienten
    this.grad = (coeffizient.length)-1;
    System.out.println("Koeffizienten eingeben!");
    for(int i=0; i<(grad+1);i++)
      this.coeffizient[i] = Eingabe.intValue();
  public void show() // Methode zum Ausgeben des Polynoms
    for (int i=0; i<(this.getGrad()+1);i++)
      System.out.print(coeffizient[i] + "x^" + i + " + ");
    System.out.println();
  public int getGrad()
    return this.grad;
  public Polynom add(Polynom p) // Methode zum Addieren zweier Polynome
    System.out.println("\np:" + p.getGrad());
    System.out.println("this:" + this.getGrad());
    if(p.getGrad() >= this.getGrad()) // Vorgehen falls p.getGrad() gr��er als this.getGrad()
      q1 = new Polynom(p.getGrad());
      grad = p.getGrad();
      for(int i=0; i<(this.getGrad()+1);i++)
        q1.coeffizient[i] = this.coeffizient[i] + p.coeffizient;
for(int i=(this.getGrad()+1);i<(p.getGrad()+1);i++)
q1.coeffizient[i] = p.coeffizient[i];
else // Vorgehen falls this.getGrad() gr��er als p.getGrad()
q1 = new Polynom(this.getGrad());
grad = this.getGrad();
for(int i=0; i<(p.getGrad()+1);i++)
q1.coeffizient[i] = this.coeffizient[i] + p.coeffizient[i];
for(int i=(p.getGrad()+1);i<(this.getGrad()+1);i++)
q1.coeffizient[i] = this.coeffizient[i];
return q1; // R�ckgabe des Ergebnisspolynoms
// Diese Klasse testet die Klasse Polynom
public class Test
public static void main(String[] args)
System.out.println("Grad eingeben!");
Polynom p1 = new Polynom(Eingabe.intValue());
p1.readCoeffizients();
p1.show();
System.out.println(p1.getGrad());
System.out.println("Grad eingeben!");
Polynom p2 = new Polynom(Eingabe.intValue());
p2.readCoeffizients();
p2.show();
System.out.println(p2.getGrad());
//Polynom p3 = (p2.add(p1));
//p3.show();
(p2.add(p1)).show();
Thanks for your help!

Answer 1

Ehm, this should really be obvious: because in the
first two cases you are using the constructor
and readCoeffizients(), whereas in the third
case you are only using the constructor.You?re right, but I initiate grad in the add method.Then look again: you don't! You are calling the constructor, but the constructor is not assigning grad in a proper way. If you are refering to the line grad = p.getGrad();this is in fact equal to this.grad = p.getGrad();But this.grad is not q1.grad (which is private). Assign grad in the constructor only (where it belongs) or better still don't use grad at all and derive the degree of the polynom from the length of the coefficients array.