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.

Code :

---

 
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)
	   {
 
		System.out.println(key+pointer.value);
 
		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;
		root.num_keys++;
 
		//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

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

Code JAVA:

---

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;
}

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