feat: Add Java Search Suggestions project

.gitignore

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+# Java
+*.class
+*.log
+*.jar
+*.war
+*.ear
+# Build directories
+target/
+build/
+out/
+bin/
+# Editor temporary files
+*.swp
+*~
+# IDE files
+.idea/
+.vscode/
+*.iml
+*.iws
+*.ipr
+# Other
+.DS_Store
+Thumbs.db

Search suggestion system/README.md

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+# Java Search Suggestions System (Trie)
+
+This is a simple and efficient command-line implementation of a search suggestions system (autocomplete) in Java. It uses a **Trie (Prefix Tree)** data structure to store a dictionary of words and find all words that match a given prefix.
+
+This project is a clean, single-file implementation suitable for demonstrating the practical application of a Trie.
+
+## Features
+
+* **Trie-Based:** Uses a `TrieNode` class with a `HashMap` for efficient, case-insensitive prefix lookups.
+* **Case-Insensitive:** All inserted words and prefixes are handled in lowercase.
+* **Interactive:** Includes a `main` method that allows you to load a dictionary and test prefixes in real-time.
+* **Loads from File:** Reads its dictionary from an external `dictionary.txt` file.
+
+## How to Compile and Run
+
+This project consists of a single Java file and a dictionary text file.
+
+**1. Compile the Code:**
+Open your terminal in the project directory and run:
+
+```bash
+javac SearchSuggestions.java
+```
+
+**2. Run the Program:**
+After compiling, run the program:
+
+```bash
+java SearchSuggestions
+```
+
+**3. Example Session:**
+The program will first load the words from `dictionary.txt`.
+
+```text
+Loading dictionary from 'dictionary.txt'...
+Successfully loaded 10 words.
+
+Enter prefix to search (or 'q' to quit): pro
+Suggestions for 'pro':
+ -> profile
+ -> program
+ -> project
+ -> python
+
+Enter prefix to search (or 'q' to quit): app
+Suggestions for 'app':
+ -> app
+ -> apple
+ -> apply
+ -> application
+
+Enter prefix to search (or 'q' to quit): q
+Goodbye!
+```
+
+## How It Works
+
+* `TrieNode`: A private inner class holds a `Map<Character, TrieNode>` for its children and a `boolean` to mark the end of a word.
+* `insert(String word)`: Iterates through each character of the word, creating new nodes in the Trie as needed.
+* `getSuggestions(String prefix)`:
+  1.  Traverses the Trie to the node corresponding to the last character of the prefix.
+  2.  If the prefix path doesn't exist, it returns an empty list.
+  3.  If it does, it calls a recursive helper `findAllWords()` to explore all child paths from that node and collect all complete words.

Search suggestion system/SearchSuggestions.java

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+import java.io.BufferedReader;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Scanner;
+
+public class SearchSuggestions {
+
+    private class TrieNode {
+        Map<Character, TrieNode> children = new HashMap<>();
+        boolean isEndOfWord;
+    }
+
+    private final TrieNode root;
+
+    public SearchSuggestions() {
+        root = new TrieNode();
+    }
+
+    public void insert(String word) {
+        if (word == null || word.isEmpty()) {
+            return;
+        }
+        TrieNode node = root;
+        for (char c : word.toLowerCase().toCharArray()) {
+            node = node.children.computeIfAbsent(c, k -> new TrieNode());
+        }
+        node.isEndOfWord = true;
+    }
+
+    public List<String> getSuggestions(String prefix) {
+        if (prefix == null) {
+            return Collections.emptyList();
+        }
+        String lowerPrefix = prefix.toLowerCase();
+        TrieNode node = root;
+
+        for (char c : lowerPrefix.toCharArray()) {
+            node = node.children.get(c);
+            if (node == null) {
+                return Collections.emptyList();
+            }
+        }
+
+        List<String> suggestions = new ArrayList<>();
+        findAllWords(node, new StringBuilder(lowerPrefix), suggestions);
+        return suggestions;
+    }
+
+    private void findAllWords(TrieNode node, StringBuilder currentWord, List<String> suggestions) {
+        if (node.isEndOfWord) {
+            suggestions.add(currentWord.toString());
+        }
+
+        for (Map.Entry<Character, TrieNode> entry : node.children.entrySet()) {
+            currentWord.append(entry.getKey());
+            findAllWords(entry.getValue(), currentWord, suggestions);
+            currentWord.setLength(currentWord.length() - 1); // Backtrack
+        }
+    }
+
+    /**
+     * Loads words from a specified dictionary file into the Trie.
+     */
+    private static int loadDictionary(SearchSuggestions trie, String filename) {
+        int wordCount = 0;
+        // The dictionary file is inside the same folder, so the path is simple.
+        try (BufferedReader br = new BufferedReader(new FileReader(filename))) {
+            String line;
+            while ((line = br.readLine()) != null) {
+                if (!line.trim().isEmpty()) {
+                    trie.insert(line.trim());
+                    wordCount++;
+                }
+            }
+        } catch (FileNotFoundException e) {
+            System.err.println("Error: Dictionary file not found: " + filename);
+        } catch (IOException e) {
+            System.err.println("Error: Failed to read dictionary file: " + e.getMessage());
+        }
+        return wordCount;
+    }
+
+    public static void main(String[] args) {
+        SearchSuggestions trie = new SearchSuggestions();
+
+        // Looks for the file in the same directory as the .java file.
+        // When running, you must be "inside" this folder.
+        String dictionaryFile = "dictionary.txt";
+        System.out.println("Loading dictionary from '" + dictionaryFile + "'...");
+
+        int wordCount = loadDictionary(trie, dictionaryFile);
+
+        if (wordCount == 0) {
+            System.err.println("Dictionary is empty or could not be loaded. Exiting.");
+            return;
+        }
+
+        System.out.println("Successfully loaded " + wordCount + " words.");
+
+        try (Scanner scanner = new Scanner(System.in)) {
+
+        while (true) {
+            System.out.print("\nEnter prefix to search (or 'q' to quit): ");
+            String prefix = scanner.nextLine();
+
+            if (prefix.equalsIgnoreCase("q") || prefix.isEmpty()) {
+                break;
+            }
+
+            List<String> suggestions = trie.getSuggestions(prefix);
+
+            if (suggestions.isEmpty()) {
+                System.out.println("No suggestions found for '" + prefix + "'.");
+            } else {
+                System.out.println("Suggestions for '" + prefix + "':");
+                for (String suggestion : suggestions) {
+                    System.out.println(" -> " + suggestion);
+                }
+            }
+        }
+    }
+    System.out.println("Goodbye!");
+    }
+}

Search suggestion system/dictionary.txt

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+apple
+app
+application
+apply
+apricot
+banana
+band
+bank
+bat
+project
+program
+profile
+java
+javascript
+react
+node
+sql
+system
+search
+suggestion
+trie
+tree