Untitled

package lab;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Scanner;

public class Lab08 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        Deque<String> backStack = new ArrayDeque<>();
        Deque<String> forwardStack = new ArrayDeque<>();

        String input = "";

        while (!"Home".equals(input = scanner.nextLine())) {
            if ("back".equals(input)) {
                if (backStack.size() > 1) {
                    forwardStack.push(backStack.pop());
                    String currentURL = backStack.peek();
                    System.out.println(currentURL);
                } else {
                    System.out.println("no previous URLs");
                }
            } else if ("forward".equals(input)) {
                if (!forwardStack.isEmpty()) {
                    backStack.push(forwardStack.peek());
                    System.out.println(forwardStack.poll());
                } else {
                    System.out.println("no next URLs");
                }
            } else {
                if (!forwardStack.isEmpty()) {
                    forwardStack.clear();
                }
                backStack.push(input);
                System.out.println(backStack.peek());
            }
        }

    }
}