Stack Using Linked List in Java — Tutorial, Code, and Examples

1) What is a Stack?

A stack is a linear data structure that follows LIFO — Last In, First Out. Push adds an item to the top; Pop removes the most recent item. Linked Lists make stacks dynamic, without a fixed array size.

Why Linked List? No fixed capacity, O(1) push/pop, and no resizing needed.

2) Step 1 — The `Node` Class

Each node stores a value and a pointer to the next node. New nodes become the new top.

class Node {
    int val;
    Node next;  // pointer to next node

    Node(int val) {
        this.val = val;
        this.next = null; // initially end of list
    }
}

3) Step 2 — The `stack_linklist` Class

We keep a reference to the top node. Push adds a new node on top; Pop removes the top node; Peek returns the top value without removal.

public class stack_linklist {
    private Node top; // points to the top of the stack

    public stack_linklist() {
        this.top = null;
    }

    // Push: O(1)
    public void push(int v) {
        Node new_node = new Node(v);
        new_node.next = top;
        top = new_node;
        System.out.println("Pushed " + v + " into stack");
    }

    // Pop: O(1)
    public int pop() {
        if (top == null) {
            System.out.println("Stack is empty");
            return -1;
        }
        int v = top.val;
        top = top.next;
        return v;
    }

    // Peek: O(1)
    public int peek() {
        if (top == null) {
            System.out.println("Stack is empty");
            return -1;
        }
        return top.val;
    }

    public boolean isEmpty() {
        return top == null;
    }

    public void display() {
        if (top == null) {
            System.out.println("Stack is empty");
            return;
        }
        System.out.print("Stack elements (top to bottom): ");
        Node t = top;
        while (t != null) {
            System.out.print(t.val + " ");
            t = t.next;
        }
        System.out.println();
    }

    public static void main(String[] args) {
        stack_linklist stk = new stack_linklist();
        stk.push(5);
        stk.push(7);
        stk.push(3);
        stk.push(8);
        stk.display();

        System.out.println("Popped: " + stk.pop()); // 8
        System.out.println("Popped: " + stk.pop()); // 3
        System.out.println("Popped: " + stk.pop()); // 7
        System.out.println("Popped: " + stk.pop()); // 5
        System.out.println("Popped: " + stk.pop()); // empty
    }
}

Tip: Return -1 for empty pops in demo code, but in production prefer throwing EmptyStackException for clarity.

4) How Push/Pop Works (Mental Model)

Push: create a node → point its next to current top → reassign top to this node.
Pop: read top.val → move top down to top.next → return the value.

Common bug: Forgetting new_node.next = top will break the chain and lose the rest of the stack.

5) Practice Problems

Reverse a String: push characters, pop to rebuild reversed string.
Balanced Parentheses: push '(' and pop on ')'; stack must be empty at the end.
Postfix Evaluation: push numbers, pop two on operator, compute, push result.
Decimal to Binary: push remainders of division by 2, then pop to print.
Undo/Redo Simulation: two stacks — one for undo, one for redo.

6) Full Source (Single File)

Copy this single file into stack_linklist.java and run it.

class Node {
    int val;
    Node next;
    Node(int val) { this.val = val; this.next = null; }
}

public class stack_linklist {
    private Node top;
    public stack_linklist() { this.top = null; }

    public void push(int v) {
        Node n = new Node(v);
        n.next = top;
        top = n;
    }
    public int pop() {
        if (top == null) return -1;
        int v = top.val;
        top = top.next;
        return v;
    }
    public int peek() {
        if (top == null) return -1;
        return top.val;
    }
    public boolean isEmpty() { return top == null; }

    public static void main(String[] args) {
        stack_linklist s = new stack_linklist();
        s.push(5); s.push(7); s.push(3); s.push(8);
        System.out.println("Popped: " + s.pop());
        System.out.println("Popped: " + s.pop());
        System.out.println("Popped: " + s.pop());
        System.out.println("Popped: " + s.pop());
        System.out.println("Popped: " + s.pop());
    }
}

7) Next Steps

Add size() and clear() methods.
Convert to a generic stack: class Stack<T>.
Implement a min stack that returns the minimum element in O(1).

1) What is a Stack?

2) Step 1 — The Node Class

3) Step 2 — The stack_linklist Class

4) How Push/Pop Works (Mental Model)

5) Practice Problems

6) Full Source (Single File)

7) Next Steps

2) Step 1 — The `Node` Class

3) Step 2 — The `stack_linklist` Class