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Thread: array element declaring problem

  1. #1
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    Default array element declaring problem

    <code>public class mHandler
    {


    public static int num=4;


    ...............
    ...........
    .........
    ......
    public static void main(String[] args)
    {


    some code}



    }


    public class A

    {
    int num;
    B aList[]=new B[num];



    }





    public class B
    {

    int x;
    int y;

    public B(int a,int b)
    {
    this.x=a;
    this.y=b;


    }

    }







    </code>


    although i have defined num as global variable, i can not define the arrays using num in the array element brackets like [num] in the class A.. Specifically aList[num] is not defined
    Last edited by jack_nutt; July 29th, 2011 at 09:22 PM.


  2. #2
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    Default Re: array element declaring problem

    Perhaps the 'num' in the nested class is being confused with 'num' in mHandler. 'num' in your nested class (class A) is not defined. Try changing it to int num = 4;

  3. #3
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    Default Re: array element declaring problem

    i know, but how can i define num once such that i dont have to change it in the other calsses by declaring its value?

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    Default Re: array element declaring problem

    but how can i define num once
    To define the variable num only once, remove the "int num" line:
    public class A
     
    {
    int num; // Remove this line it is a second definition of num

    Please edit your code and wrap it in code tags. Unformatted code is hard to read. See: http://www.javaprogrammingforums.com...do=bbcode#code

    If you get compile errors, please copy and paste here the full text.
    Last edited by Norm; July 30th, 2011 at 06:55 AM.

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    Default Re: array element declaring problem

     
     
    public class mHand {
     
    	/**
    	 * @param args
    	 */public static int num =3;
    	public static void main(String[] args) {
     
    	b m=new b();
    	c g=new c();
    	m.aList[0]=g;
     
    	System.out.println(m.aList[0].x);
     
     
    		// TODO Auto-generated method stub
     
    	}
     
    }
     
     
    public class b {
    int x,y;
     
    	c aList[]=new c[num];
     
     
     
    }                    
     
     
    public class c {
     
     
    	int x=2;;
    	int y=3;
     
    }


    error come on line :
    c aList[]=new c[num];

    num cannot be resolved to a variable
    Last edited by jack_nutt; July 31st, 2011 at 10:27 PM.

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    Default Re: array element declaring problem

    You have declared num in class mHand. Class B does not know anything about it. Think about different rooms in a building. I'm standing in one room with a number written on a piece of paper. You are in a different room at the other end of the building. Can you see what is written on my piece of paper?
    Improving the world one idiot at a time!

  7. #7
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    Default Re: array element declaring problem

    how can i make num visible in the other class?

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    Default Re: array element declaring problem

    If you have declared it static (which is a bad idea in my opinion) you would access it classname.variablename.

    If you make it non-static then class b would need to instantiate an object of mHand and then access it directly or via a method.
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    Default Re: array element declaring problem

    mHand could pass the value of num to b in b's constructor

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    Default Re: array element declaring problem

     
    public class mHand {
     
    	/**
    	 * @param args
    	 */public static int num =3;
    	public static void main(String[] args) {
     
    	b m=new b(num);
    	c g=new c();
    	m.aList[0]=g;
     
    	System.out.println(m.aList[0].x);
     
     
    		// TODO Auto-generated method stub
     
    	}
     
    }
     
     
     
     
    public class b {
    int x,y;
    	int num;
    	c aList[]=new c[num];
     
    	public b(int num)
    	{
    		this.num=num;
     
    	}
     
    }
     
     
    public class c {
     
     
    	int x=2;;
    	int y=3;
     
    }


    even i declare num in b's constructor the aList is not created



    Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
    at mHand.main(mHand.java:11)


    >> m.aList[0]=g;

  11. #11
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    Default Re: array element declaring problem

    ArrayIndexOutOfBoundsException: 0
    The array does not have 1 element (the 0th)
    Where do you give a size/number of dimensions to the aList array? Is the size value > 0?

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    Default Re: array element declaring problem

    Try creating the array after you assign a value to num.
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