Improve TrieImp.java comments, add unit tests and enhance readability

DIRECTORY.md

@@ -727,6 +727,7 @@
               * [SameTreesCheckTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/SameTreesCheckTest.java)
               * [SplayTreeTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/SplayTreeTest.java)
               * [TreeTestUtils](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/TreeTestUtils.java)
+              * [TrieImpTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/TrieImpTest.java)
               * [VerticalOrderTraversalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/VerticalOrderTraversalTest.java)
               * [ZigzagTraversalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/trees/ZigzagTraversalTest.java)
           * divideandconquer

src/main/java/com/thealgorithms/datastructures/trees/TrieImp.java

@@ -1,19 +1,35 @@
 package com.thealgorithms.datastructures.trees;
 
-import java.util.Scanner;
-
 /**
- * Trie Data structure implementation without any libraries
+ * Trie Data structure implementation without any libraries.
+ * <p>
+ * The Trie (also known as a prefix tree) is a special tree-like data structure
+ * that is used to store a dynamic set or associative array where the keys are
+ * usually strings. It is highly efficient for prefix-based searches.
+ * <p>
+ * This implementation supports basic Trie operations like insertion, search,
+ * and deletion.
+ * <p>
+ * Each node of the Trie represents a character and has child nodes for each
+ * possible character.
  *
  * @author <a href="https://github.com/dheeraj92">Dheeraj Kumar Barnwal</a>
  */
 public class TrieImp {
 
+    /**
+     * Represents a Trie Node that stores a character and pointers to its children.
+     * Each node has an array of 26 children (one for each letter from 'a' to 'z').
+     */
     public class TrieNode {
 
         TrieNode[] child;
         boolean end;
 
+        /**
+         * Constructor to initialize a TrieNode with an empty child array
+         * and set end to false.
+         */
         public TrieNode() {
             child = new TrieNode[26];
             end = false;
@@ -22,10 +38,22 @@ public TrieNode() {
 
     private final TrieNode root;
 
+    /**
+     * Constructor to initialize the Trie.
+     * The root node is created but doesn't represent any character.
+     */
     public TrieImp() {
         root = new TrieNode();
     }
 
+    /**
+     * Inserts a word into the Trie.
+     * <p>
+     * The method traverses the Trie from the root, character by character, and adds
+     * nodes if necessary. It marks the last node of the word as an end node.
+     *
+     * @param word The word to be inserted into the Trie.
+     */
     public void insert(String word) {
         TrieNode currentNode = root;
         for (int i = 0; i < word.length(); i++) {
@@ -39,6 +67,16 @@ public void insert(String word) {
         currentNode.end = true;
     }
 
+    /**
+     * Searches for a word in the Trie.
+     * <p>
+     * This method traverses the Trie based on the input word and checks whether
+     * the word exists. It returns true if the word is found and its end flag is
+     * true.
+     *
+     * @param word The word to search in the Trie.
+     * @return true if the word exists in the Trie, false otherwise.
+     */
     public boolean search(String word) {
         TrieNode currentNode = root;
         for (int i = 0; i < word.length(); i++) {
@@ -52,6 +90,17 @@ public boolean search(String word) {
         return currentNode.end;
     }
 
+    /**
+     * Deletes a word from the Trie.
+     * <p>
+     * The method traverses the Trie to find the word and marks its end flag as
+     * false.
+     * It returns true if the word was successfully deleted, false if the word
+     * wasn't found.
+     *
+     * @param word The word to be deleted from the Trie.
+     * @return true if the word was found and deleted, false if it was not found.
+     */
     public boolean delete(String word) {
         TrieNode currentNode = root;
         for (int i = 0; i < word.length(); i++) {
@@ -69,75 +118,26 @@ public boolean delete(String word) {
         return false;
     }
 
+    /**
+     * Helper method to print a string to the console.
+     *
+     * @param print The string to be printed.
+     */
     public static void sop(String print) {
         System.out.println(print);
     }
 
     /**
-     * Regex to check if word contains only a-z character
+     * Validates if a given word contains only lowercase alphabetic characters
+     * (a-z).
+     * <p>
+     * The method uses a regular expression to check if the word matches the pattern
+     * of only lowercase letters.
+     *
+     * @param word The word to be validated.
+     * @return true if the word is valid (only a-z), false otherwise.
      */
     public static boolean isValid(String word) {
         return word.matches("^[a-z]+$");
     }
-
-    public static void main(String[] args) {
-        TrieImp obj = new TrieImp();
-        String word;
-        @SuppressWarnings("resource") Scanner scan = new Scanner(System.in);
-        sop("string should contain only a-z character for all operation");
-        while (true) {
-            sop("1. Insert\n2. Search\n3. Delete\n4. Quit");
-            try {
-                int t = scan.nextInt();
-                switch (t) {
-                case 1:
-                    word = scan.next();
-                    if (isValid(word)) {
-                        obj.insert(word);
-                    } else {
-                        sop("Invalid string: allowed only a-z");
-                    }
-                    break;
-                case 2:
-                    word = scan.next();
-                    boolean resS = false;
-                    if (isValid(word)) {
-                        resS = obj.search(word);
-                    } else {
-                        sop("Invalid string: allowed only a-z");
-                    }
-                    if (resS) {
-                        sop("word found");
-                    } else {
-                        sop("word not found");
-                    }
-                    break;
-                case 3:
-                    word = scan.next();
-                    boolean resD = false;
-                    if (isValid(word)) {
-                        resD = obj.delete(word);
-                    } else {
-                        sop("Invalid string: allowed only a-z");
-                    }
-                    if (resD) {
-                        sop("word got deleted successfully");
-                    } else {
-                        sop("word not found");
-                    }
-                    break;
-                case 4:
-                    sop("Quit successfully");
-                    System.exit(1);
-                    break;
-                default:
-                    sop("Input int from 1-4");
-                    break;
-                }
-            } catch (Exception e) {
-                String badInput = scan.next();
-                sop("This is bad input: " + badInput);
-            }
-        }
-    }
 }

src/test/java/com/thealgorithms/datastructures/trees/TrieImpTest.java

@@ -0,0 +1,76 @@
+package com.thealgorithms.datastructures.trees;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class TrieImpTest {
+    private TrieImp trie;
+
+    @BeforeEach
+    public void setUp() {
+        trie = new TrieImp();
+    }
+
+    @Test
+    public void testInsertAndSearchBasic() {
+        String word = "hello";
+        trie.insert(word);
+        assertTrue(trie.search(word), "Search should return true for an inserted word.");
+    }
+
+    @Test
+    public void testSearchNonExistentWord() {
+        String word = "world";
+        assertFalse(trie.search(word), "Search should return false for a non-existent word.");
+    }
+
+    @Test
+    public void testInsertAndSearchMultipleWords() {
+        String word1 = "cat";
+        String word2 = "car";
+        trie.insert(word1);
+        trie.insert(word2);
+
+        assertTrue(trie.search(word1), "Search should return true for an inserted word.");
+        assertTrue(trie.search(word2), "Search should return true for another inserted word.");
+        assertFalse(trie.search("dog"), "Search should return false for a word not in the Trie.");
+    }
+
+    @Test
+    public void testDeleteExistingWord() {
+        String word = "remove";
+        trie.insert(word);
+        assertTrue(trie.delete(word), "Delete should return true for an existing word.");
+        assertFalse(trie.search(word), "Search should return false after deletion.");
+    }
+
+    @Test
+    public void testDeleteNonExistentWord() {
+        String word = "nonexistent";
+        assertFalse(trie.delete(word), "Delete should return false for a non-existent word.");
+    }
+
+    @Test
+    public void testInsertAndSearchPrefix() {
+        String prefix = "pre";
+        String word = "prefix";
+        trie.insert(prefix);
+        trie.insert(word);
+
+        assertTrue(trie.search(prefix), "Search should return true for an inserted prefix.");
+        assertTrue(trie.search(word), "Search should return true for a word with the prefix.");
+        assertFalse(trie.search("pref"), "Search should return false for a prefix that is not a full word.");
+    }
+
+    @Test
+    public void testIsValidWord() {
+        assertTrue(TrieImp.isValid("validword"), "Word should be valid (only lowercase letters).");
+        assertFalse(TrieImp.isValid("InvalidWord"), "Word should be invalid (contains uppercase letters).");
+        assertFalse(TrieImp.isValid("123abc"), "Word should be invalid (contains numbers).");
+        assertFalse(TrieImp.isValid("hello!"), "Word should be invalid (contains special characters).");
+        assertFalse(TrieImp.isValid(""), "Empty string should be invalid.");
+    }
+}