Write a method called countLeftNodes that returns the number of left children in the tree. A left child is a node that appears as the root of the left-hand subtree of another node. For example, reference tree #1 has 3 left children (the nodes storing the values 5, 1, and 4).

Please also create the main method to test the code.

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IntTree.java

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} }

// post: prints the tree contents using a preorder traversal public void printPreorder() { System.out.print("preorder:"); printPreorder(overallRoot); System.out.println(); }

// post: prints the tree contents using a preorder traversal // post: prints in preorder the tree with given root private void printPreorder(IntTreeNode root) { if (root != null) { System.out.print(" " + root.data); printPreorder(root.left); printPreorder(root.right); } }

// post: prints the tree contents using a inorder traversal public void printInorder() { System.out.print("inorder:"); printInorder(overallRoot); System.out.println(); }

// post: prints in inorder the tree with given root private void printInorder(IntTreeNode root) { if (root != null) { printInorder(root.left); System.out.print(" " + root.data); printInorder(root.right); } }

// post: prints the tree contents using a postorder traversal public void printPostorder() { System.out.print("postorder:"); printPostorder(overallRoot); System.out.println(); }

// post: prints in postorder the tree with given root private void printPostorder(IntTreeNode root) { if (root != null) { printPostorder(root.left); printPostorder(root.right); System.out.print(" " + root.data); } }

// post: prints the tree contents, one per line, following an // inorder traversal and using indentation to indicate // node depth; prints right to left so that it looks // correct when the output is rotated. public void printSideways() { printSideways(overallRoot, 0); }

// post: prints in reversed preorder the tree with given // root, indenting each line to the given level private void printSideways(IntTreeNode root, int level) { if (root != null) { printSideways(root.right, level + 1); for (int i = 0; i

}

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IntTreeNode.java

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// Class for storing a single node of a binary tree of ints

public class IntTreeNode { public int data; public IntTreeNode left; public IntTreeNode right; // constructs a leaf node with given data public IntTreeNode(int data) { this(data, null, null); } // constructs a branch node with given data, left subtree, // right subtree public IntTreeNode(int data, IntTreeNode left, IntTreeNode right) { this.data = data; this.left = left; this.right = right; } }

Reference Tree #1