Trees program in java

Actually, very cleeaaaaar explanation, but why did not you separate the node implementation from the Tree implementation, That woul be much better. Thanks for your comments. I omitted the Tree Class as I find that serving no purpose other than holding the root Node. You can add all the methods to the Node class that would be needed for performing any operation on the tree. How would you remove all the leaf nodes of this tree? Thanks for helping.

Here is a simple implementation to delete all the leaf nodes under a node. If you look at the diagram here. You would see that is child of 11 and is also child of As it is child of 11, we add it to According to the naming convention i followed in this tutorial, if had 2 children, their names would be and Great article, thank you so much!

Could you please tell me what would be the most efficient way to check if a node already exists anywhere in the structure? For example by name if we assume that node data is a String. The best way is usually to have a map of the node data. You can just lookup the map to find if the data is in the tree rather than looking all the nodes for data.

I have this method below as function to fill out;. Please help with my problem, thanks. This can just be accomplished with some changes to the print method we have shown in the article. Thanks a ton for the great explanation. The following snapshots show the results of setting the JTree.

No matter what the look and feel, the default icon displayed by a node is determined by whether the node is a leaf and, if not, whether it is expanded. For example, in the Windows and Motif look and feel implementations, the default icon for each leaf node is a dot; in the Java look and feel, the default leaf icon is a paper-like symbol.

In all the look-and-feel implementations we have shown, branch nodes are marked with folder-like symbols. Some look and feels might have different icons for expanded branches versus collapsed branches.

You can easily change the default icon used for leaf, expanded branch, or collapsed branch nodes. To do so, you first create an instance of DefaultTreeCellRenderer. You could always create your own TreeCellRenderer implementation from scratch, reusing whatever components you like. Next, specify the icons to use by invoking one or more of the following methods on the renderer: setLeafIcon for leaf nodes , setOpenIcon for expanded branch nodes , setClosedIcon for collapsed branch nodes.

If you want the tree to display no icon for a type of node, then specify null for the icon. Once you have set up the icons, use the tree's setCellRenderer method to specify that the DefaultTreeCellRenderer paint its nodes.

Here is an example, taken from TreeIconDemo. If you want finer control over the node icons or you want to provide tool tips, you can do so by creating a subclass of DefaultTreeCellRenderer and overriding the getTreeCellRendererComponent method. The following code, from TreeIconDemo2. The renderer also specifies tool-tip text, as the bold lines show. You might be wondering how a cell renderer works. When a tree paints each node, neither the JTree nor its look-and-feel-specific implementation actually contains the code that paints the node.

Instead, the tree uses the cell renderer's painting code to paint the node. For example, to paint a leaf node that has the string "The Java Programming Language", the tree asks its cell renderer to return a component that can paint a leaf node with that string.

If the cell renderer is a DefaultTreeCellRenderer , then it returns a label that paints the default leaf icon followed by the string. A cell renderer only paints; it cannot handle events. If you want to add event handling to a tree, you need to register your handler on either the tree or, if the handling occurs only when a node is selected, the tree's cell editor. For information about cell editors, see Concepts: Editors and Renderers. That section discusses table cell editors and renderers, which are similar to tree cell editors and renderers.

The following figure shows an application called DynamicTreeDemo that lets you add nodes to and remove nodes from a visible tree. You can also edit the text in each node. By explicitly creating the tree's model, the code guarantees that the tree's model is an instance of DefaultTreeModel. That way, we know all the methods that the tree model supports.

For example, we know that we can invoke the model's insertNodeInto method, even though that method is not required by the TreeModel interface. To make the text in the tree's nodes editable, we invoke setEditable true on the tree. Note that although DefaultMutableTreeNode has methods for changing a node's content, changes should go through the DefaultTreeModel cover methods. Otherwise, the tree model events would not be generated, and listeners such as the tree would not know about the updates.

To be notified of node changes, we can implement a TreeModelListener. Here is an example of a tree model listener that detects when the user has typed in a new name for a tree node:.

Here is the code that the Add button's event handler uses to add a new node to the tree:. The code creates a node, inserts it into the tree model, and then, if appropriate, requests that the nodes above it be expanded and the tree scrolled so that the new node is visible. To insert the node into the model, the code uses the insertNodeInto method provided by the DefaultTreeModel class. If DefaultTreeModel does not suit your needs, then you will need to write a custom data model.

Your data model must implement the TreeModel interface. TreeModel specifies methods for getting a particular node of the tree, getting the number of children of a particular node, determining whether a node is a leaf, notifying the model of a change in the tree, and adding and removing tree model listeners. Interestingly, the TreeModel interface accepts any kind of object as a tree node.

It does not require that nodes be represented by DefaultMutableTreeNode objects, or even that nodes implement the TreeNode interface. Interview Questions. Company Questions. Artificial Intelligence. Cloud Computing. Data Science. Angular 7. Machine Learning. Data Structures. Operating System. Computer Network. Compiler Design.

Computer Organization. Discrete Mathematics. Ethical Hacking. Computer Graphics. Software Engineering. Web Technology. Cyber Security. C Programming. Control System. Data Mining. Data Warehouse. Javatpoint Services JavaTpoint offers too many high quality services. Some factors are considered for choosing the data structure: What type of data needs to be stored? Cost of operations: If we want to minimize the cost for the operations for the most frequently performed operations.

For example, we have a simple list on which we have to perform the search operation; then, we can create an array in which elements are stored in sorted order to perform the binary search.

The binary search works very fast for the simple list as it divides the search space into half. Memory usage: Sometimes, we want a data structure that utilizes less memory.

Suppose we want to show the employees and their positions in the hierarchical form then it can be represented as shown below: The above tree shows the organization hierarchy of some company. Let's understand some key points of the Tree data structure.

A tree data structure is defined as a collection of objects or entities known as nodes that are linked together to represent or simulate hierarchy. A tree data structure is a non-linear data structure because it does not store in a sequential manner.

It is a hierarchical structure as elements in a Tree are arranged in multiple levels. In the Tree data structure, the topmost node is known as a root node. Each node contains some data, and data can be of any type. In the above tree structure, the node contains the name of the employee, so the type of data would be a string. Each node contains some data and the link or reference of other nodes that can be called children. Some basic terms used in Tree data structure.

Let's consider the tree structure, which is shown below: In the above structure, each node is labeled with some number. Root: The root node is the topmost node in the tree hierarchy. In other words, the root node is the one that doesn't have any parent.

In the above structure, node numbered 1 is the root node of the tree. If a node is directly linked to some other node, it would be called a parent-child relationship. Each node stores a value. Below, we take two classes; one is Node representing a node in the tree, and the other is the JavaTree class that performs operations on the nodes. The Node class has three variables, first is the value to store in the node that is of int data type. Then we take two variables, for left and right child nodes; both the variables are of Node type.

We make a constructor of the Node class and initialize the value from the parameter; the left and right variables are set as null. In the JavaTree class, we take a variable of type Node and call it root. Then we create a method traverseRecursionTree that takes a Node as a parameter, and inside the method, we check if the node is null ; if it is not, then we call the traverseRecursionTree method from itself and pass the left part of node.