Create 1 Stack using LL.java

Author: JayakrishnaThota

3 LinkedLists/1 Stack using LL.java

@@ -0,0 +1,66 @@
+package Stacks;
+import java.util.*;
+
+public class LinkedListImplementation {
+    ListNode head;
+    int size;
+    public static class ListNode{
+        int val;
+        ListNode next;
+        public ListNode(){
+            this.next = null;
+        }
+        public ListNode(int val){
+            this.val = val;
+            this.next = null;
+        }
+    }
+
+    public LinkedListImplementation(){
+        head = new ListNode();
+        size = 0;
+    }
+
+    //O(1)
+    //Insert at the beginning in a singly linked list
+    public void push(int x){
+        size++;
+        ListNode newnode = new ListNode(x);
+        newnode.next = head;
+        head = newnode;
+        System.out.println(x+" is pushed onto the stack");
+    }
+
+    //O(1)
+    //Delete from beginning of a linked list
+    public int pop(){
+        int ret = head.val;
+        //Delete head
+        head = head.next;
+        size--;
+        System.out.println(ret+"is popped from the stack");
+        return ret;
+    }
+
+    public int peek(){
+        return head.val;
+    }
+
+    public boolean isEmpty(){
+        return (size==0);
+    }
+
+    public int size(){
+        return size;
+    }
+
+    public static void main(String[] args) {
+        LinkedListImplementation l = new LinkedListImplementation();
+        l.push(4);
+        l.push(5);
+        System.out.println(l.peek());
+        System.out.println(l.pop());
+        System.out.println(l.size());
+        System.out.println(l.isEmpty());
+    }
+}