style: fix Checkstyle violations in AVLInsert.java

Author: darshan-totagi

src/test/java/com/thealgorithms/tree/AVLtree/AVLInsert.java

@@ -1,8 +1,10 @@
 package com.thealgorithms.tree.AVLtree;
 
 class Node {
-    int key, height;
-    Node left, right;
+    int key;
+    int height;
+    Node left;
+    Node right;
 
     Node(int d) {
         key = d;
@@ -14,59 +16,85 @@ public class AVLInsert {
 
     Node root;
 
-    int height(Node n) {
-        return n == null ? 0 : n.height;
+    int height(Node node) {
+        if (node == null) {
+            return 0;
+        }
+        return node.height;
     }
 
-    int getBalance(Node n) {
-        return n == null ? 0 : height(n.left) - height(n.right);
+    int getBalance(Node node) {
+        if (node == null) {
+            return 0;
+        }
+        return height(node.left) - height(node.right);
     }
 
     Node rightRotate(Node y) {
         Node x = y.left;
-        Node T2 = x.right;
+        Node t2 = x.right;
+
+        // Perform rotation
         x.right = y;
-        y.left = T2;
+        y.left = t2;
+
+        // Update heights
         y.height = Math.max(height(y.left), height(y.right)) + 1;
         x.height = Math.max(height(x.left), height(x.right)) + 1;
+
+        // Return new root
         return x;
     }
 
     Node leftRotate(Node x) {
         Node y = x.right;
-        Node T2 = y.left;
+        Node t2 = y.left;
+
+        // Perform rotation
         y.left = x;
-        x.right = T2;
+        x.right = t2;
+
+        // Update heights
         x.height = Math.max(height(x.left), height(x.right)) + 1;
         y.height = Math.max(height(y.left), height(y.right)) + 1;
+
+        // Return new root
         return y;
     }
 
     Node insert(Node node, int key) {
-        if (node == null)
+        if (node == null) {
             return new Node(key);
+        }
 
-        if (key < node.key)
+        if (key < node.key) {
             node.left = insert(node.left, key);
-        else if (key > node.key)
+        } else if (key > node.key) {
             node.right = insert(node.right, key);
-        else
-            return node;
+        } else {
+            return node; // Duplicate keys not allowed
+        }
 
         node.height = 1 + Math.max(height(node.left), height(node.right));
         int balance = getBalance(node);
 
-        if (balance > 1 && key < node.left.key)
+        // Left Left Case
+        if (balance > 1 && key < node.left.key) {
             return rightRotate(node);
+        }
 
-        if (balance < -1 && key > node.right.key)
+        // Right Right Case
+        if (balance < -1 && key > node.right.key) {
             return leftRotate(node);
+        }
 
+        // Left Right Case
         if (balance > 1 && key > node.left.key) {
             node.left = leftRotate(node.left);
             return rightRotate(node);
         }
 
+        // Right Left Case
         if (balance < -1 && key < node.right.key) {
             node.right = rightRotate(node.right);
             return leftRotate(node);
@@ -93,7 +121,7 @@ public static void main(String[] args) {
         tree.root = tree.insert(tree.root, 50);
         tree.root = tree.insert(tree.root, 25);
 
-        System.out.println("Preorder traversal of AVL tree:");
+        System.out.println("Preorder traversal of constructed tree is:");
         tree.preOrder(tree.root);
     }
 }