Java null pointer exception on if statement

Question

I have following if statement:

if (node.left.left == null && node.left.right != null)

Related to a binary tree. Before this if statement I have a other if statement that checks if node.left is null.

Why am I getting null pointer exception on this statement?

Full code in the method up until the exception:

 BinaryTreeNode node= root;


if (root==null)
    return true;
else
    {
        while(node!=null)
        {
        if (node.key>key && node.left !=null)
        {
            if (node.left.key==key)
                {
                    if(node.left.left==null && node.left.right==null)
                        node.left=null;
                    if(node.left.left==null && node.left.right!=null)
                        node.left=node.left.right;

Could you show us the exact error message and your `node.left` check? My guess is that the check doesn't work out. — Hubert Grzeskowiak, Oct 24 '17 at 01:57
Show both statements, not just one of them. Also, please make this a MCVE; as is we have no way to try it ourselves. — Elliott Frisch, Oct 24 '17 at 01:57

score 4 · Answer 1 · answered Oct 24 '17 at 02:03

4

                    node.left=null;
                if(node.left.left==null && node.left.right!=null)
                    node.left=node.left.right

You are explicitly setting node.left to null.

answered Oct 24 '17 at 02:03

D M

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Java null pointer exception on if statement

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