private void removeInternalEntry()

in src/main/java/org/apache/commons/collections4/trie/AbstractPatriciaTrie.java [2184:2258]
47 lines of code
13 McCabe index (conditional complexity)

    private void removeInternalEntry(final TrieEntry<K, V> h) {
        if (h == root) {
            throw new IllegalArgumentException("Cannot delete root Entry!");
        }
        if (!h.isInternalNode()) {
            throw new IllegalArgumentException(h + " is not an internal Entry!");
        }

        final TrieEntry<K, V> p = h.predecessor;

        // Set P's bitIndex
        p.bitIndex = h.bitIndex;

        // Fix P's parent, predecessor and child Nodes
        {
            final TrieEntry<K, V> parent = p.parent;
            final TrieEntry<K, V> child = p.left == h ? p.right : p.left;

            // if it was looping to itself previously,
            // it will now be pointed from its parent
            // (if we aren't removing its parent --
            //  in that case, it remains looping to itself).
            // otherwise, it will continue to have the same
            // predecessor.
            if (p.predecessor == p && p.parent != h) {
                p.predecessor = p.parent;
            }

            if (parent.left == p) {
                parent.left = child;
            } else {
                parent.right = child;
            }

            if (child.bitIndex > parent.bitIndex) {
                child.parent = parent;
            }
        }

        // Fix H's parent and child Nodes
        {
            // If H is a parent of its left and right child
            // then change them to P
            if (h.left.parent == h) {
                h.left.parent = p;
            }

            if (h.right.parent == h) {
                h.right.parent = p;
            }

            // Change H's parent
            if (h.parent.left == h) {
                h.parent.left = p;
            } else {
                h.parent.right = p;
            }
        }

        // Copy the remaining fields from H to P
        //p.bitIndex = h.bitIndex;
        p.parent = h.parent;
        p.left = h.left;
        p.right = h.right;

        // Make sure that if h was pointing to any uplinks,
        // p now points to them.
        if (isValidUplink(p.left, p)) {
            p.left.predecessor = p;
        }

        if (isValidUplink(p.right, p)) {
            p.right.predecessor = p;
        }
    }