Thread: Binary Search Tree in Java [HELP]

Hi guys,
This is a Java Implementation of Binary Search Tree

import java.io.*;
 
class node {
 
    int data;
    public node left;
    public node right;
 
    public node(int elem) {
        data = elem;
        left = null;
        right = null;
    }
}
 
public class bst {
 
    node root;
    int choice, left, right, elem;
    InputStreamReader ip;
    BufferedReader br;
    int parent;
 
    public bst() 
	{
        choice = 0;
        root = null;
        ip = new InputStreamReader(System.in);
        br = new BufferedReader(ip);
    }
 
    public void input_element() {
        System.out.println("enter the element");
        try {
            String x = br.readLine();
            elem = Integer.parseInt(x);
        } catch (IOException e) {
            System.out.println("exception in input");
        }
    }
 
    public void inorder(node p) {
        if (p != null) {
            inorder(p.left);
            System.out.println(p.data);
            inorder(p.right);
        }
    }
 
    public void preorder(node p) {
        if (p != null) {
            System.out.println(p.data);
            preorder(p.left);
            preorder(p.right);
        }
    }
 
    public void postorder(node p) {
        if (p != null) {
            postorder(p.left);
            postorder(p.right);
            System.out.println(p.data);
        }
    }
 
    public node insert(node root) {
        if (root == null) {
            root = new node(elem);
        } else if (root.data < elem) {
            root.right = insert(root.right);
        } else if (root.data > elem) {
            root.left = insert(root.left);
        }
        return root;
    }
 
    public node delete(node root) {
        if (root != null) {
            if (root.data < elem) {
                root.right = delete(root.right);
            } else if (root.data > elem) {
                root.left = delete(root.left);
            } else if (root.left == null) {
                root = root.right;
            } else if (root.right == null) {
                root = root.left;
            } else {
                elem = deletemin(root.right);
                root.data = elem;
                root.right = delete(root.right);
            }
            return root;
        }
        return root;
    }
 
    public int deletemin(node root) {
        if (root.left == null) {
            return root.data;
        } else {
            return deletemin(root.left);
        }
    }
 
    public void findparent(node root) {
        if (root == null) {
            parent = -1;
            return;
        }
        if (root.data == elem) {
            return;
        }
        parent = root.data;
        if (root.data > elem) {
            findparent(root.left);
        } else if (root.data < elem) {
            findparent(root.right);
        }
    }
 
    public void findchildren(node root) {
        if (root == null) {
            left = right = -1;
            return;
        }
        if (root.data == elem) {
            left = right = 0;
            if (root.left != null) {
                left = root.left.data;
            }
            if (root.right != null) {
                right = root.right.data;
            }
        }
        if (root.data > elem) {
            findchildren(root.left);
        } else if (root.data < elem) {
            findchildren(root.right);
        }
    }
 
    public void search() {
        parent = 0;
        input_element();
        findparent(root);
        if (parent != -1) {
            if (parent == 0) {
                System.out.println(elem + "is present as the root node");
            } else {
                System.out.println(elem + "is present as the child of" + parent);
            }
        }
    }
 
    public void findtype() {
        parent = 0;
        left = right = 0;
        input_element();
        findparent(root);
        if (parent != -1) {
            if (parent == 0) {
                System.out.println(elem + "is the root node");
                return;
            } else {
                if (parent > elem) {
                    System.out.println(elem + "is present as left child of" + parent);
                } else {
                    System.out.println(elem + "is present as the right child of " + parent);
                }
            }
            if ((root.left == null) && (root.right == null)) {
                System.out.println(elem + "is present as the leaf node");
            }
            if (root.left != null) {
                System.out.println("left child is" + left);
            }
            if (root.right != null) {
                System.out.println("rignt child is" + right);
            }
        }
    }
 
    public void getchoice() {
        System.out.println("menu\n");
        System.out.println("1.inser\n2.delete\n3.inorder\n4.preorder\n5.postorder\n6.find parent\n7.find node\n8.find type\n9.exit\n");
        System.out.println("enter the choice\t");
        try {
            String x = br.readLine();
            choice = Integer.parseInt(x);
        } catch (IOException e) {
            System.out.println("incorrect choice");
        }
 
        switch (choice) {
            case 1:
                input_element();
                root = insert(root);
                break;
            case 2:
                input_element();
                root = delete(root);
                break;
            case 3:
                inorder(root);
                break;
            case 4:
                preorder(root);
                break;
            case 5:
                postorder(root);
                break;
            case 6:
                parent = 0;
                input_element();
                findparent(root);
                if (parent == -1) {
                    System.out.println("element not present\n");
                } else if (parent == 0) {
                    System.out.println(elem + "is at root\n");
                } else {
                    System.out.println("parent of" + elem + "is" + parent);
                }
                break;
            case 7:
                search();
                break;
            case 8:
                findtype();
                break;
            case 9:
                System.exit(0);
                break;
            default:
                System.out.println("wrong choice");
                break;
        }
    }
 
    public static void main(String args[]) {
        bst m;
        m = new bst();
        while (true) {
            m.getchoice();
            System.out.println("\n");
        }
    }
}

Im a C++ programmer new to Java. Though the code runs fine(not checked it fully), i dont know if there is some deprecated features or errors in the code since im a beginner. Also suggest some good programming practices related to the code. Thanks in advance

In the future, please post your code here directly. Many people are suspicious of links elsewhere.

I've copied your code here and put it into a highlight box. If you're unsure how to do this yourself, please see my signature.

One thing I would recommend with your code is to separate all direct user interaction from your bst class. This allows your class to be more general and can be used by any interface you decide to design.

Secondly, I would recommend renaming certain things in your code. The default Java convention is to use CamelCase.

Classes/interfaces/enumerations begin with uppercase letters, and variable names/method names begin with lowercase letters. Also, It's general convention to spell out the name so it's clear what the name describes. Each subsequent word in an identifier is capitalized. For example, bst could be BinarySearchTree (though BST could be acceptable too since a lot of people will know what you mean by BST), and getchoice would become getChoice.

Lastly, add some comments (both Javadoc and regular).

Javadoc comments are used to let other people (or even yourself) know how to use your code, and describe the "contract" that that particular class/method fulfills. The other comments are mainly for you (or if someone else is going to be looking at/changing your code, them too) to be able to come back and quickly understand what the code is doing.

I don't see any deprecated features or errors (but I only did a quick glance). The best way to find any possible errors is to test your code for general use, and also for "boundary cases" (such as trying to add two of the same item).