Create LinkedList.java

DataStructures/LinkedList.java

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+/**
+ * Linked List Implementation in Java
+ * 
+ * A Linked List is a linear data structure where elements (nodes) 
+ * are connected using references (pointers). Each node contains:
+ *   - data (value)
+ *   - next (reference to next node)
+ *
+ * Advantages:
+ *  - Dynamic size (no need to define capacity)
+ *  - Easy insertion/deletion at any position
+ *
+ * Disadvantages:
+ *  - Random access not possible (must traverse sequentially)
+ *  - Uses extra memory (pointer/reference for each node)
+ *
+ * Example:
+ * Insert 10 → Insert 20 → Insert 30
+ * Linked List: 10 -> 20 -> 30
+ * Delete 20
+ * Linked List: 10 -> 30
+ */
+
+class LinkedList {
+
+    // Node class: represents a single element in Linked List
+    static class Node {
+        int data;
+        Node next;
+
+        Node(int data) {
+            this.data = data; // store value
+            this.next = null; // initially no link
+        }
+    }
+
+    Node head; // head (first node of the list)
+
+    // Insert new node at the end
+    public void insert(int data) {
+        Node newNode = new Node(data);
+
+        if (head == null) {
+            head = newNode; // if list is empty
+        } else {
+            Node temp = head;
+            while (temp.next != null) { // traverse till last node
+                temp = temp.next;
+            }
+            temp.next = newNode; // link new node at end
+        }
+    }
+
+    // Delete a node by value
+    public void delete(int key) {
+        Node temp = head, prev = null;
+
+        // If head itself holds the key
+        if (temp != null && temp.data == key) {
+            head = temp.next; // move head
+            return;
+        }
+
+        // Search for the key
+        while (temp != null && temp.data != key) {
+            prev = temp;
+            temp = temp.next;
+        }
+
+        // If key not found
+        if (temp == null) return;
+
+        // Unlink the node
+        prev.next = temp.next;
+    }
+
+    // Search an element
+    public boolean search(int key) {
+        Node temp = head;
+        while (temp != null) {
+            if (temp.data == key) return true;
+            temp = temp.next;
+        }
+        return false;
+    }
+
+    // Display the linked list
+    public void display() {
+        Node temp = head;
+        while (temp != null) {
+            System.out.print(temp.data + " -> ");
+            temp = temp.next;
+        }
+        System.out.println("null");
+    }
+
+    // Main method to test LinkedList
+    public static void main(String[] args) {
+        LinkedList list = new LinkedList();
+
+        // Insert elements
+        list.insert(10);
+        list.insert(20);
+        list.insert(30);
+        System.out.println("After Insertion:");
+        list.display();  // 10 -> 20 -> 30 -> null
+
+        // Delete element
+        list.delete(20);
+        System.out.println("After Deletion of 20:");
+        list.display();  // 10 -> 30 -> null
+
+        // Search element
+        System.out.println("Search 30: " + list.search(30)); // true
+        System.out.println("Search 50: " + list.search(50)); // false
+    }
+}