| I’m developing a Spring Boot application that stores a tree structure in PostgreSQL. The table schema is: CREATE TABLE nodes ( id BIGINT PRIMARY KEY, value VARCHAR(150), parent_id BIGINT ); Example data: 1 |
Management |
NULL 2 |
IT Department |
1 3 |
Developer |
2 To rebuild the tree in memory, I’m using Java Collections: private final Map > tree = new HashMap<>(); public void loadTree(List nodes) { for (NodeEntity node : nodes) { if (node.getParentId() != null) { tree.putIfAbsent(node.getParentId(), new ArrayList<>()); tree.get(node.getParentId()).add(node.getId()); } } } The problem is that |
