Breaking out of a recursion method in java

Question

How to save "flag" when i set it. For exemple, when i am in block

if (hashFunction(value) == hashFunction(node.value))
{

    flag = true;
    return flag; 

}

in debug flag = true, but next step and pointer is in

if (hashFunction(value) < hashFunction(node.value))
    {
        if (node.left != null)
        {

            findPrivate(value, node.left);------THERE

        } else
        {
            flag = false;
            return flag;
        }
    }

And in result, my method return false. How to fix it? Sorry for my english. Full code is bellow.

    private boolean findPrivate(T value, Node node)
{

    if (node == null)
    {
        flag = false;
        return flag;

    }
    if (hashFunction(value) == hashFunction(node.value))
    {

        flag = true;
        return flag; 

    }

    if (hashFunction(value) > hashFunction(node.value))
    {
        if (node.rigth != null)
        {
            findPrivate(value, node.rigth);
        } else
        {

            flag = false;
            System.out.println("value= " + value + " " + flag);
            return flag;
        }
    }

    if (hashFunction(value) < hashFunction(node.value))
    {
        if (node.left != null)
        {

            findPrivate(value, node.left);

        } else
        {
            flag = false;
            return flag;
        }
    }
    return flag;
}

Answer 1

The problem is that when you recurse, you're ignoring the return value:

findPrivate(value, node.left);

I haven't looked in detail, but you may well just be able to change each occurrence of that to:

return findPrivate(value, node.left);

I would also suggest removing your flag variable completely - it's not clear where it's declared anyway, but it looks like it should probably not be used; instead, just return the value directly. For example:

if (node.left != null)
{
    return findPrivate(value, node.left);
} else
{
    return false;
}

... which can then be easily refactored to:

return node.left != null ? findPrivate(value, node.left) : false;

And in fact, as you already return false if node is null, you can just use:

return findPrivate(value, node.left);

in that case. I suspect you can refactor your code pretty simply along those lines...

Answer 2

You need to return the value from the recursive call:

private static final class Node<T> {

    protected T value;
    protected Node<T> right;
    protected Node<T> left;

    private boolean findPrivate(T value, Node<T> node) {
        if (node == null) {
            return false;
        }
        if (hashFunction(value) == hashFunction(node.value)) {
            return true;
        }
        if (hashFunction(value) > hashFunction(node.value)) {
            if (node.right != null) {
                return findPrivate(value, node.right);
            } else {
                return false;
            }
        }
        if (hashFunction(value) < hashFunction(node.value)) {
            if (node.left != null) {
                return findPrivate(value, node.left);
            } else {
                return false;
            }
        }
        throw new UnsupportedOperationException("cannot compare hashCodes");
    }

    private int hashFunction(T value) {
        //stuff
    }
}

You do not need to actually save a flag , you just need to return the value.