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Thread: NullPointerException @@

  1. #1
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    Default NullPointerException @@

    package assignment;
    import java.util.*;
    import java.util.Stack;
     
    public class Assignment {
     
       public static void main(String[] args) {
            // TODO code application logic here
            boolean exit = false;
            boolean flag = false;
            MyArrayList<GenericStack[][]>region = new MyArrayList<>();
            Container container = new Container();
            GenericStack<Container>[][]storage=new GenericStack[10][10];
     
         while(exit == false){
            System.out.println("Please select the function that you want to preform");
            System.out.println("1) Load Container into region");
            System.out.println("2) Unload the container from the region");
            Scanner input = new Scanner(System.in);
            int selection = input.nextInt();
            //switch case to select option
            switch(selection){
                case 1 : LoadObject( storage, container);
                    break;
                default: System.out.println("Please key in the correct input :");
     
            }//end of the switch case
            //option for exit
            while(flag==true)
            System.out.println("Do you want to exit ? (Y/N))");
            Scanner inputExit = new Scanner(System.in);
            if(inputExit.nextInt()=='Y' || inputExit.nextInt()== 'y')
                exit = true;
            else 
                if( inputExit.nextInt()=='N' || inputExit.nextInt()=='n')
                    exit = false;
                else {
                   //If the user key in a non-valid input
                    System.out.print("Please key in the correct input.");
                    flag =true;
                }
            } 
        }//end of thw while loop
     
        public static void LoadObject(GenericStack[][]storage, Container container){
     
            System.out.println("How many container");
            Scanner input = new Scanner(System.in);
            int counter = input.nextInt();
            int i, j;
     
            for(i = 0; i <10 ; i++){
                for(j = 0 ; j< 10 ; j++){
                    if(counter>0){
                        if(!storage[i][j].isEmpty()){             //<--------
                            for(i = storage[i][j].getSize() ; i < 10 ; i++ ){
                                System.out.println("Please key in the container id :\n");
                                int objectId = input.nextInt();
                                container.SetObjectId(objectId);
                                System.out.println("Please key in the container description :\n");
                                String objectDesc = input.nextLine();
                                container.SetObjectDesc(objectDesc);
                                storage[i][j].push(container);
                                counter--;
                                 }//end of the insertion
                            }
                         }//end of the number of container
                       else
                            i = 10; j =10;//end the check empty if is finish container
                        }//end of the for loop
                    }//end of the for loop
                }
     
     
         }



    Here is part of my coding @@
    i have no idea why there is a "NullPointerException" error when i run it. I have no idea what it is please help me.
    Last edited by jps; August 21st, 2013 at 05:54 PM. Reason: code tags


  2. #2
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    Default Re: NullPointerException @@

    Please post your code in code tags.

    Why the '@@'? Is that relevant?

    If you're getting errors you want help with, post the exact error, the entire error and stack trace, copied and pasted from just as it appears at your end. If possible, post a short, runnable code example that demonstrates the error.

    I believe your problem is because arrays are created with null elements until otherwise initialized. The storage[][] array is full of nulls.

  3. #3
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    Default Re: NullPointerException @@

    Quote Originally Posted by GregBrannon View Post
    Why the '@@'? Is that relevant?
    Some sort of annoying emoticon perhaps.
    Improving the world one idiot at a time!

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