LinkedStack.java

package com.examplehub.datastructures.stack;

import com.examplehub.datastructures.linkedlist.Node;
import java.util.EmptyStackException;
import java.util.StringJoiner;

public class LinkedStack<E> {

  /** The top of the stack. */
  private Node<E> top;

  /** The size of the stack. */
  private int size;

  /** Constructor. */
  public LinkedStack() {
    top = null;
    size = 0;
  }

  /**
   * Added to element to the top of the stack.
   *
   * @param element the element to be added.
   * @return {@code true} if added successfully.
   */
  public boolean push(E element) {
    Node<E> newNode = new Node<>(element);
    if (top != null) {
      newNode.next = top;
    }
    top = newNode;
    size++;
    return true;
  }

  /**
   * Remove element from the top of the stack.
   *
   * @return top element of the stack.
   * @throws EmptyStackException if the stack is empty.
   */
  public E pop() {
    if (empty()) {
      throw new EmptyStackException();
    }
    E retValue = top.data;
    top = top.next;
    size--;
    return retValue;
  }

  /**
   * Peek the top element of the stack.
   *
   * @return the top element of the stack.
   * @throws EmptyStackException if the stack is empty.
   */
  public E peek() {
    if (empty()) {
      throw new EmptyStackException();
    }
    return top.data;
  }

  /**
   * Test if the stack is empty.
   *
   * @return {@code true} if the stack is empty, otherwise {@code false}.
   */
  public boolean empty() {
    return top == null;
  }

  /** Remove all elements of the stack. */
  public void clear() {
    top = null;
    size = 0;
  }

  /**
   * Return size of the stack.
   *
   * @return size of the stack.
   */
  public int size() {
    return size;
  }

  @Override
  public String toString() {
    StringJoiner joiner = new StringJoiner(", ", "[", "]");
    Node<E> temp = top;
    while (temp != null) {
      joiner.add(temp.data.toString());
      temp = temp.next;
    }
    return joiner.toString();
  }
}