One thing I have always found lacking in Java collections\/containers is TreeMap. A simple class that takes a hierarchical approach to mapping data to a node. Given a hierarchical string like “\/java\/myapp\/javafx\/config\/phone” I can set the various objects relative to this on that node.<\/p>\n
Java Preferences() class supports this hierarchical approach but it is limited to native data types. I have never understood why this has been missing from the JRE. So I created my own implementation and here it is for anyone else looking.<\/p>\n
Here is the code to let you place any kind of object on a specified node.<\/p>\n\n\n
package name.mymiller.extensions.containers;\n\nimport java.util.ArrayList;\nimport java.util.Collection;\nimport java.util.HashMap;\nimport java.util.List;\n\n\/**\n * @param <T> Type of Object to map\n * @author jmiller\n * Class used to map values out on a tree. Allows for infinite depth. Key names should be in form of\n * \"\/text\/text\/text\/....\"\n *\/\npublic class TreeMap<T> {\n\n \/**\n * Roote Node of the tree also known as \"\/\"\n *\/\n private TreeNode root = null;\n\n \/**\n * Adds the Value to the node at specified Key\n *\n * @param key Specified branch to add values to\n * @param value Values to add at node\n *\/\n public void add(String key, T value) {\n TreeNode node = this.findNode(key);\n\n ArrayList<T> values = node.getValues();\n if (values == null) {\n values = new ArrayList<>();\n node.setValues(values);\n }\n\n values.add(value);\n }\n\n \/**\n * Add Collection of values to the specified node\n *\n * @param key Specifies the node to add values to.\n * @param collection Collection of values to add to the node.\n * @return\n *\/\n public boolean addAll(String key, Collection<? extends T> collection) {\n TreeNode node = this.findNode(key);\n\n ArrayList<T> values = node.getValues();\n if (values == null) {\n values = new ArrayList<T>();\n node.setValues(values);\n }\n\n return values.addAll(collection);\n }\n\n \/**\n * Remove the colleciton of values from the specified node\n *\n * @param key Specifies the node to remove values from.\n * @param collection Collection of values to remove.\n * @return Boolean indicating if values remoted.\n *\/\n public boolean removeAll(String key, Collection<?> collection) {\n TreeNode node = this.findNode(key);\n\n ArrayList<T> values = node.getValues();\n if (values == null) {\n return false;\n }\n\n return values.removeAll(collection);\n }\n\n \/**\n * Remove a value from specified node\n *\n * @param key Specified node to remove value from\n * @param value Valueto remove from specified node.\n * @return boolean indicating success.\n *\/\n public boolean remove(String key, T value) {\n TreeNode node = this.findNode(key);\n ArrayList<T> values = node.getValues();\n\n if (values == null) {\n return false;\n }\n\n return values.remove(value);\n }\n\n \/**\n * Clear all values from specified node\n *\n * @param key Node to clear all values from.\n *\/\n public void clearNode(String key) {\n TreeNode node = this.findNode(key);\n ArrayList<T> values = node.getValues();\n\n if (values != null) {\n values.clear();\n }\n }\n\n \/**\n * Returns the values associated with this key, or null if none are set.\n *\n * @param key Specified Node to return values on.\n * @return List of values.\n *\/\n public List<T> get(String key) {\n TreeNode node = this.findNode(key);\n return node.getValues();\n }\n\n \/**\n * Internal method used to find\/create the tree structure to the specified node\n *\n * @param key Node to create\/find\n * @return Node specified\n *\/\n private TreeNode findNode(String key) {\n String[] keys = key.split(\"\/\");\n\n TreeNode currentNode = null;\n for (String nodeKey : keys) {\n if (nodeKey.isEmpty()) {\n if (this.root == null) {\n this.root = new TreeNode();\n }\n currentNode = this.root;\n } else if (currentNode == null) {\n if (this.root == null) {\n this.root = new TreeNode();\n }\n currentNode = this.root;\n }\n\n if (!nodeKey.isEmpty()) {\n HashMap<String, TreeNode> children = currentNode.getChildren();\n if (children == null) {\n currentNode.setChildren(new HashMap<>());\n children = currentNode.getChildren();\n } else {\n currentNode = children.get(nodeKey);\n }\n\n if (currentNode == null) {\n currentNode = new TreeNode();\n children.put(nodeKey, currentNode);\n }\n }\n }\n return currentNode;\n }\n\n \/**\n * Internal class used to map out tree structure and hold values.\n *\n * @author jmiller\n *\/\n private class TreeNode {\n \/**\n * Values of this branch holds\n *\/\n private ArrayList<T> values = null;\n\n \/**\n * Map directing to the children of this branch.\n *\/\n private HashMap<String, TreeNode> children = null;\n\n \/**\n * Get the values of the current Node\n *\n * @return ArrayList of the values on this node\n *\/\n public ArrayList<T> getValues() {\n return values;\n }\n\n \/**\n * Sets the values of this node.\n *\n * @param values ArrayList containing the values of this node.\n *\/\n public void setValues(ArrayList<T> values) {\n this.values = values;\n }\n\n \/**\n * @return Get the HashMap that has the children of this node.\n *\/\n public HashMap<String, TreeNode> getChildren() {\n return children;\n }\n\n \/**\n * Sets the HashMap for this node, with the children\n *\n * @param children Hashmap of the children of this node.\n *\/\n public void setChildren(HashMap<String, TreeNode> children) {\n this.children = children;\n }\n }\n\n}\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"One thing I have always found lacking in Java collections\/containers is TreeMap. A simple class that takes a hierarchical approach to mapping data to a node. Given a hierarchical string like “\/java\/myapp\/javafx\/config\/phone” I can set the various objects relative to this on that node. Java Preferences() class supports this hierarchical approach but it is limited […]<\/p>\n","protected":false},"author":1,"featured_media":2238,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[457],"tags":[69],"series":[248],"class_list":["post-2233","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java_extra","tag-java-2","series-advanced-classes"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/www.mymiller.name\/wordpress\/wp-content\/uploads\/2018\/04\/tree-3097419_640.jpg?fit=640%2C360&ssl=1","jetpack-related-posts":[{"id":3179,"url":"https:\/\/www.mymiller.name\/wordpress\/java_extra\/understanding-json-data-processing-with-java-exploring-the-jsonfieldprocessor-class\/","url_meta":{"origin":2233,"position":0},"title":"Understanding JSON Data Processing with Java: Exploring the JsonFieldProcessor Class","author":"Jeffery Miller","date":"January 15, 2026","format":false,"excerpt":"In today's digital era, data comes in various formats, with JSON (JavaScript Object Notation) being one of the most popular for representing structured data. 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