Implementing a binary tree data struct in java

Question

I'm trying to implement a binary tree data structure in java. This is my code. I'm very new to java and don't quite understand where my errors are. Thank you. I got this error message: binTree.java:21: error: class, interface, or enum expected

class Node { int value; Node left; Node right; Node(int value) { this.value = value; right = null; left = null; } } public class BinTree { Node root; } private Node addRecursive(Node current, int value) { if (current == null) { return new Node(value); } if (value < current.value) { current.left = addRecursive(current.left, value); } else if (value > current.value) { current.right = addRecursive(current.right, value); } else { // value already exists return current; } return current; } public void add(int value) { root = addRecursive(root, value); } System.out.println(); System.out.println("testcase 1:"); BinTree binTree2 = new BinTree(); binTree2.insertNode(new Node(3)); binTree2.insertNode(new Node(201)); binTree2.insertNode(new Node(60)); binTree2.insertNode(new Node(30)); binTree2.insertNode(new Node(45)); binTree2.treeWalk();

Fix your indentation and check your braces. In Java you can't have methods outside of a class, and you can't have statements outside of a method or initializer block. — Radiodef
– Radiodef, Commented Jul 9, 2018 at 23:38
Check this for complete step by step: baeldung.com/java-binary-tree — Sergei Sirik
– Sergei Sirik, Commented Jul 9, 2018 at 23:57

Sami Tahri · Accepted Answer · 2018-07-09 23:43:57Z

You used a closing bracket at the line 21 just after the Node root field where you shouldn't Also, you will need a main methods or Junit tedt case to launch your test (at the bottom, starting before your System.out.println())

wade king · Accepted Answer · 2018-07-09 23:49:09Z

your methods need to be placed inside of the class BinTree and the code you want to execute needs to be wrapped in a main function like so

public class BinTree { Node root; private Node addRecursive(Node current, int value) { if (current == null) { return new Node(value); } if (value < current.value) { current.left = addRecursive(current.left, value); } else if (value > current.value) { current.right = addRecursive(current.right, value); } else { // value already exists return current; } return current; } public void add(int value) { root = addRecursive(root, value); } public static void main(String []args){ System.out.println(); System.out.println("testcase 1:"); BinTree binTree2 = new BinTree(); binTree2.insertNode(new Node(3)); binTree2.insertNode(new Node(201)); binTree2.insertNode(new Node(60)); binTree2.insertNode(new Node(30)); binTree2.insertNode(new Node(45)); binTree2.treeWalk(); } }

It looks like you're missing some methods like insertNode and treeWalk but it should compile after you have implemented those.

Thank you! Second question: How would I implement those methods?

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