НЛ Лаб4

import java.util.Date;
import java.util.LinkedList;
import java.util.Scanner;

class Node<T> {
    T element;
    Node<T> next;
    Node<T> prev;

    public Node(T element, Node<T> next, Node<T> prev) {
        this.element = element;
        this.next = next;
        this.prev = prev;
    }
}

class Stack<T> {
    Node<T> first;
    Node<T> current;

    public Stack() {
        first = null;
        current = first;
    }

    public void push(T element) {
        if (first == null) {
            first = new Node<T>(element, null, null);
            current = first;
        } else {
            current.next = new Node<T>(element, null, current);
            current = current.next;
        }
    }

    public T peek() {
        return current.element;
    }

    public T pop() {
        if (current != null) {
            T tmp = current.element;
            if (current.prev != null) {
                current = current.prev;
                current.next = null;
            } else {
                current = null;
            }
            return tmp;
        }
        return null;
    }

    public boolean isEmpty() {
        if (current == null)
            return true;
        return false;
    }
}

public class StackTest {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner jin = new Scanner(System.in);
        int k = jin.nextInt();
        if (k == 0) {
            int n = jin.nextInt();
            Stack<Integer> stack = new Stack<Integer>();
            for (int i = 1; i <= n; ++i) {
                if (i > 1)
                    System.out.print(" ");
                System.out.print(i);
                stack.push(i);
            }
            System.out.println();
            for (int i = n; i >= 1; --i) {
                if (i < n)
                    System.out.print(" ");
                System.out.print(stack.pop());
            }
            System.out.println();
        }
        if (k == 1) {
            int n = jin.nextInt();
            Stack<String> stack = new Stack<String>();
            for (int i = 0; i < n; ++i) {
                if (i > 0)
                    System.out.print(" ");
                String next = jin.next();
                System.out.print(next);
                stack.push(next);
            }
            System.out.println();
            for (int i = 0; i < n; ++i) {
                if (i > 0)
                    System.out.print(" ");
                System.out.print(stack.pop());
            }
        }
        if (k == 2) {
            Stack<Double> stack = new Stack<Double>();
            while (jin.hasNextDouble()) {
                stack.push(jin.nextDouble());
            }
            int i = 0;
            while (!stack.isEmpty()) {
                if (i > 0)
                    System.out.print(" ");
                ++i;
                System.out.print(stack.pop());
            }
        }
        if (k == 3) {
            int n = jin.nextInt();
            Stack<Long> stack = new Stack<Long>();
            LinkedList<Long> control_stack = new LinkedList<Long>();
            boolean exact = true;
            for (int i = 0; exact && i < n; ++i) {
                if (Math.random() < 0.5) {// add
                    long to_add = (long) (Math.random() * 456156168);
                    stack.push(to_add);
                    control_stack.addFirst(to_add);
                } else {
                    exact &= control_stack.isEmpty() == stack.isEmpty();
                    if (exact && !stack.isEmpty()) {
                        if (Math.random() > 0.7)
                            exact &= control_stack.removeFirst().equals(
                                    stack.pop());
                        else
                            exact &= control_stack.peekFirst().equals(
                                    stack.peek());
                    }
                }
            }
            System.out.println(exact);
        }
        if (k == 4) {
            Stack<Date> test_stack = new Stack<Date>();
            System.out.println(test_stack.isEmpty());
            try {
                test_stack.pop();
            } catch (Exception e) {
                System.out.println(e.getClass().getSimpleName());
            }
            try {
                test_stack.peek();
            } catch (Exception e) {
                System.out.println(e.getClass().getSimpleName());
            }
        }
    }
}