Need Help with a program

[Jere Johnson]

hello,
I get this program to compile , but my error message is the following when
i try to run the program.
Exception in thread "main" java.lang.NullPointerException
at SeqOfIntegers.insert(SeqOfIntegers.java:80)
at SeqOfIntegers.main(SeqOfIntegers.java:28)
Press any key to continue...

 /**
 *  SeqOfIntegers tests the VectorSequence and LinkedSequence
 *
 */
public class SeqOfIntegers
{
VectorSequence seq;
//LinkedSequence seq;


//constructor for SeqOfIntegers
public SeqOfIntegers() {
VectorSequence seq = new VectorSequence ();
//LinkedSequence seq = new LinkedSequence ();
}
public static void main(String[] args){
SeqOfIntegers s = new SeqOfIntegers();
s.insert(5);
s.insert(4);
s.insert(9);
s.insert(8);
s.insert(13);
s.insert(1);
s.print();
s.remove(5);
s.remove(7);
s.remove(12);
if (s.find(13))
  System.out.println("The number 13 is found");
else
  System.out.println("The number 13 is not found");
s.print();
 } // end of static method

  /**
   * Purpose: boolean method to find an integer
   * @param - i
   *value of the integer to find
   * @precondition
   *   isCurrent() returns true.
   * @return
   *   true if i is found in sequence
   *false if i is not found in sequence
   **/
public boolean find(int i){

Integer I = new Integer (i); //wrapper
seq.start();
if (seq.getCurrent().equals(I) )
return true;
else
return false;
}
/**
   * Purpose: Inserts an Integer in the Sequence in numerical order
   * @param - i
   *value of the integer to find
   * @precondition
   *   isCurrent() returns true.
   * @return
   *   inserts the integer in the sequence
   *
   **/
public void insert(int i){

Integer I = new Integer (i); //wrapper
if (seq.getCurrent() == null){     //    Here is line 80 where error is occuring
seq.start();
seq.addAfter(I);}

else 
seq.addAfter(I);

// else if (i < seq.getCurrent())
//  seq.addBefore(I);

//else if (i >= seq.getCurrent())
//seq.addAfter(I);

}
/**
   * Purpose: method removes an Integer from the sequence
   * @param - i
   *value of the integer to remove
   * @precondition
   *   isCurrent() returns true.
   * @return
   *   removes Integer
   * @exception IllegalArgumentException
   *if Integer is not there
   *
   **/
public void remove(int i){
Integer I = new Integer (i); //wrapper
if (seq.getCurrent().equals(I))
seq.removeCurrent();
else
throw new IllegalArgumentException ("Integer not found");
}
/**
   * Purpose: Prints the entire sequence on the screen
   * @precondition
   *   isCurrent() is true
   * @return
   *   Prints sequence
   * @exception IllegalArgumentException
   *if there are no Integers in sequence
   *
   **/
public void print(){
for (seq.start(); seq.isCurrent(); seq.advance())
System.out.println (seq.getCurrent());
}

} // end of SeqOfIntegers
 

[ October 31, 2003: Message edited by: Jere Johnson ]

[Herb Schildt]

Jere:
In your code shown here:

public SeqOfIntegers() {
  VectorSequence seq = new VectorSequence ();
  //LinkedSequence seq = new LinkedSequence ();
}

You are assigning a reference to the new VectorSequence to a local reference named seq, not to the seq instance variable that you declared earlier. Try this instead:

public SeqOfIntegers() {
  seq = new VectorSequence (); // <----notice change here
  //LinkedSequence seq = new LinkedSequence ();
}

[ October 31, 2003: Message edited by: Herb Schildt ]

[Jere Johnson]

Thank you for your help. That worked!