// Java program to Implement a stack
// using singly linked list
// import package
import static java.lang.System.exit;
// Create Stack Using Linked list
class StackUsingLinkedlist {
// A linked list node
private class Node {
int data; // integer data
Node link; // reference variable Node type
}
// create global top reference variable global
Node top;
// Constructor
StackUsingLinkedlist()
{
this.top = null;
}
// Utility function to add an element x in the stack
public void push(int x) // insert at the beginning
{
// create new node temp and allocate memory
Node temp = new Node();
// check if stack (heap) is full. Then inserting an
// element would lead to stack overflow
if (temp == null) {
System.out.print("
Heap Overflow");
return;
}
// initialize data into temp data field
temp.data = x;
// put top reference into temp link
temp.link = top;
// update top reference
top = temp;
}
// Utility function to check if the stack is empty or not
public boolean isEmpty()
{
return top == null;
}
// Utility function to return top element in a stack
public int peek()
{
// check for empty stack
if (!isEmpty()) {
return top.data;
}
else {
System.out.println("Stack is empty");
return -1;
}
}
// Utility function to pop top element from the stack
public void pop() // remove at the beginning
{
// check for stack underflow
if (top == null) {
System.out.print("
Stack Underflow");
return;
}
// update the top pointer to point to the next node
top = (top).link;
}
public void display()
{
// check for stack underflow
if (top == null) {
System.out.printf("
Stack Underflow");
exit(1);
}
else {
Node temp = top;
while (temp != null) {
// print node data
System.out.printf("%d->", temp.data);
// assign temp link to temp
temp = temp.link;
}
}
}
}
// main class
public class GFG {
public static void main(String[] args)
{
// create Object of Implementing class
StackUsingLinkedlist obj = new StackUsingLinkedlist();
// insert Stack value
obj.push(11);
obj.push(22);
obj.push(33);
obj.push(44);
// print Stack elements
obj.display();
// print Top element of Stack
System.out.printf("
Top element is %d
", obj.peek());
// Delete top element of Stack
obj.pop();
obj.pop();
// print Stack elements
obj.display();
// print Top element of Stack
System.out.printf("
Top element is %d
", obj.peek());
}
}// Java program to Implement a stack
// using singly linked list
// import package
import static java.lang.System.exit;
// Create Stack Using Linked list
class StackUsingLinkedlist {
// A linked list node
private class Node {
int data; // integer data
Node link; // reference variable Node type
}
// create global top reference variable global
Node top;
// Constructor
StackUsingLinkedlist()
{
this.top = null;
}
// Utility function to add an element x in the stack
public void push(int x) // insert at the beginning
{
// create new node temp and allocate memory
Node temp = new Node();
// check if stack (heap) is full. Then inserting an
// element would lead to stack overflow
if (temp == null) {
System.out.print("
Heap Overflow");
return;
}
// initialize data into temp data field
temp.data = x;
// put top reference into temp link
temp.link = top;
// update top reference
top = temp;
}
// Utility function to check if the stack is empty or not
public boolean isEmpty()
{
return top == null;
}
// Utility function to return top element in a stack
public int peek()
{
// check for empty stack
if (!isEmpty()) {
return top.data;
}
else {
System.out.println("Stack is empty");
return -1;
}
}
// Utility function to pop top element from the stack
public void pop() // remove at the beginning
{
// check for stack underflow
if (top == null) {
System.out.print("
Stack Underflow");
return;
}
// update the top pointer to point to the next node
top = (top).link;
}
public void display()
{
// check for stack underflow
if (top == null) {
System.out.printf("
Stack Underflow");
exit(1);
}
else {
Node temp = top;
while (temp != null) {
// print node data
System.out.printf("%d->", temp.data);
// assign temp link to temp
temp = temp.link;
}
}
}
}
// main class
public class GFG {
public static void main(String[] args)
{
// create Object of Implementing class
StackUsingLinkedlist obj = new StackUsingLinkedlist();
// insert Stack value
obj.push(11);
obj.push(22);
obj.push(33);
obj.push(44);
// print Stack elements
obj.display();
// print Top element of Stack
System.out.printf("
Top element is %d
", obj.peek());
// Delete top element of Stack
obj.pop();
obj.pop();
// print Stack elements
obj.display();
// print Top element of Stack
System.out.printf("
Top element is %d
", obj.peek());
}
}