TrieEntry previousEntry()

in src/main/java/org/apache/commons/collections4/trie/AbstractPatriciaTrie.java [1971:2002]

• 28 lines of code
• 10 McCabe index (conditional complexity)

    TrieEntry<K, V> previousEntry(final TrieEntry<K, V> start) {
        if (start.predecessor == null) {
            throw new IllegalArgumentException("must have come from somewhere!");
        }

        if (start.predecessor.right == start) {
            if (isValidUplink(start.predecessor.left, start.predecessor)) {
                return start.predecessor.left;
            }
            return followRight(start.predecessor.left);
        }
        TrieEntry<K, V> node = start.predecessor;
        while (node.parent != null && node == node.parent.left) {
            node = node.parent;
        }

        if (node.parent == null) { // can be null if we're looking up root.
            return null;
        }

        if (isValidUplink(node.parent.left, node.parent)) {
            if (node.parent.left == root) {
                if (root.isEmpty()) {
                    return null;
                }
                return root;

            }
            return node.parent.left;
        }
        return followRight(node.parent.left);
    }