Updated : NaivePatternSearch.java

Author: Karthikn-VR

src/main/java/com/thealgorithms/strings/NaivePatternSearch.java

@@ -1,33 +1,44 @@
-package strings;
+package com.thealgorithms.strings;
 
 import java.util.ArrayList;
 import java.util.List;
 
-/**
- * Naive Pattern Searching algorithm.
- * Reference: https://en.wikipedia.org/wiki/String-searching_algorithm#Na%C3%AFve_string_search
- */
-public class NaivePatternSearch {
+public final class NaivePatternSearch {
+
+    // Private constructor to prevent instantiation
+    private NaivePatternSearch() {
+        throw new UnsupportedOperationException("Utility class");
+    }
 
     /**
-     * Finds all occurrences of a pattern in a given text using
-     * the naive substring search algorithm.
+     * Naive pattern searching algorithm.
      *
-     * @param text    The text in which to search.
-     * @param pattern The pattern to search for.
-     * @return List of starting indices where the pattern is found.
+     * @param text the text to be searched
+     * @param pattern the pattern to search for
+     * @return list of starting indices where pattern is found
+     * @throws IllegalArgumentException if text or pattern is null
      */
     public static List<Integer> search(String text, String pattern) {
+        if (text == null || pattern == null) {
+            throw new IllegalArgumentException("Text and pattern must not be null");
+        }
+
         List<Integer> result = new ArrayList<>();
         int n = text.length();
         int m = pattern.length();
 
         for (int i = 0; i <= n - m; i++) {
-            String sub = text.substring(i, i + m);
-            if (sub.equals(pattern)) {
+            int j;
+            for (j = 0; j < m; j++) {
+                if (text.charAt(i + j) != pattern.charAt(j)) {
+                    break;
+                }
+            }
+            if (j == m) {
                 result.add(i);
             }
         }
+
         return result;
     }
 }