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Thread: Problem with array initialization

  1. #1
    Junior Member
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    Sep 2011
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    Default Problem with array initialization

    I have been working in creating a B+ tree. I have certain problem in code. Please tell me what are the errors and how can I overcome it? I am giving the snippet where the error occurs.

    class record
    			public int value;
    		class node
    			Object[] pointers ;
    			int[] keys;
    			node parent;
    			boolean is_leaf;
    			int num_keys;
    			node next;
    			record r;
                 node start_new_tree(int key, record pointer)
    		node root = d.makeleaf();
    		root.keys[0]=key;                                        // The error is here.It gives null pointer exception
    		root.pointers[0] = (Object)pointer;
    		root.pointers[order - 1] = null;
    		root.parent = null;
    		//System.out.println(root.keys[0]+" "+root.pointers[0]+" "+root.num_keys);
    		return root;

    When I use start_new_tree in my main,this gives nullpointer exception at the place mentioned.Can you tell me how to overcome this?

    Thank you

  2. #2
    Administrator copeg's Avatar
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    Default Re: Problem with array initialization

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  3. #3
    Junior Member
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    Apr 2012
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    Default Re: Problem with array initialization

    Does method called makeleaf() initialize arrays of node class?
    For example:

    public node makeleaf(){
        node newnode = new node();
        newnode.num_keys = 5;
        // this line is important otherwise keys is null and throws NullPointerException
        newnode.keys = new int[newnode.num_keys];
        return newnode;
    Last edited by gaszabo; April 4th, 2012 at 06:01 AM.

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