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Thread: NullPointerException Error

  1. #1
    Junior Member
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    Unhappy NullPointerException Error

    Hi,

    I keep receiving a NullPointerException and have been unable to find a way to resolve it. Any assistance would be much appreciated.

    public class FitnessFrog extends Frog
    {
       // instance variable
       private int totalDistanceSprinted;
       private Random randomNumber;
       public FitnessFrog sporty1;
       public FitnessFrog sporty2;
     
       // constructor
       /**
        * Constructor for objects of class FitnessFrog.
        */
       public FitnessFrog()
       {
          super();
          this.randomNumber = new Random();      
          this.totalDistanceSprinted = 0;
       }
     
       /**
        * Setter for totalDistanceSprinted.
        */
       private void setTotalDistanceSprinted(int aValue)
       {
          this.totalDistanceSprinted = aValue;
       }
     
       /**
        * Getter for totalDistanceSprinted.
        */
       public int getTotalDistanceSprinted()
       {
          return this.totalDistanceSprinted;
       }      
     
       /**
        * Sets the value of the totalDistanceSprinted variable to 0.
        * Returns no value.
        */
       public void resetTotalDistanceSprinted()
       {
          this.setTotalDistanceSprinted(0);
       }
     
       /**
        * Returns a random integer value specifying a sprint length 
        * between 2 and 5 inclusive.
        */
       private int getSprintLength()
       {
          return (this.randomNumber.nextInt(4) + 2);
       }   
     
       /**
        * Getter for sporty1.
        */
       public FitnessFrog getSporty1()
       {
          return this.sporty1;
       }  
     
       /**
        * Getter for sporty2.
        */
       public FitnessFrog getSporty2()
       {
          return this.sporty2;
       }   
     
       /**
        *     * 
        * Saves the colour of the receiver, then sets the colour of the
        * receiver to red and gets a sprint length. Next enters a loop 
        * and on each iteration does the following: First, checks if the 
        * receiver is on the last stone (numbered 11) in which case moves 
        * the receiver to the first stone (numbered 1), otherwise moves
        * the receiver right; then increments the total distance sprinted.
        * Upon exit from the loop, casues the receiver to jump once and
        * then resets its colour. Returns no value.
        */
       public void sprint()
       {
          //save colour of the receiver
           OUColour colour1 = this.getSporty1().getColour();
           OUColour colour2 = this.getSporty2().getColour();
     
          //Set colour of receiver to red & get sprint length
         this.setColour(OUColour.RED);
         this.getSprintLength();
     
         //
         if(this.position == 11)
         {
          this.home();
         } else this.right(); this.setTotalDistanceSprinted(this.getTotalDistanceSprinted()+ getSprintLength() + 1);
     
         // Reset receivers colour
          this.getSporty1().setColour(colour1);
          this.getSporty2().setColour(colour2);
       }
     }

    Thanks,
    Steven
    Last edited by stevenroberts; May 6th, 2014 at 11:06 AM.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: NullPointerException Error

    I keep receiving a NullPointerException
    Please copy the full text of the error message and paste it here.

    Some problems I see:
    multiple statements on one line
    missing {}s for statement(s) following else
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: NullPointerException Error

    Hi Norn,

    Full error message is below:

    java.lang.NullPointerException
    in FitnessFrog.sprint(FitnessFrog.java:95)
    in Coach.train(Coach.java:99)
    in (OUWorkspace:1)


    Cheers.

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: NullPointerException Error

    java.lang.NullPointerException
    in FitnessFrog.sprint(FitnessFrog.java:95)
    There is a null value at line 95 when it is executed. Look at line 95 and find the variable with the null value and then backtrack in the code to see why the variable is null.
    If you don't understand my answer, don't ignore it, ask a question.

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