// collectiontopics/SimpleDeques.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// Very basic test of Deques
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;

class CountString implements Supplier<String> {
  private int n = 0;
  CountString() {}
  CountString(int start) { n = start; }
  @Override public String get() {
    return Integer.toString(n++);
  }
}

public class SimpleDeques {
  static void test(Deque<String> deque) {
    CountString s1 = new CountString(),
                s2 = new CountString(20);
    for(int n = 0; n < 8; n++) {
        deque.offerFirst(s1.get());
        deque.offerLast(s2.get()); // Same as offer()
    }
    System.out.println(deque);
    String result = "";
    while(deque.size() > 0) {
      System.out.print(deque.peekFirst() + " ");
      result += deque.pollFirst() + " ";
      System.out.print(deque.peekLast() + " ");
      result += deque.pollLast() + " ";
    }
    System.out.println("\n" + result);
  }
  public static void main(String[] args) {
    int count = 10;
    System.out.println("LinkedList");
    test(new LinkedList<>());
    System.out.println("ArrayDeque");
    test(new ArrayDeque<>());
    System.out.println("LinkedBlockingDeque");
    test(new LinkedBlockingDeque<>(count));
    System.out.println("ConcurrentLinkedDeque");
    test(new ConcurrentLinkedDeque<>());
  }
}
/* Output:
LinkedList
[7, 6, 5, 4, 3, 2, 1, 0, 20, 21, 22, 23, 24, 25, 26,
27]
7 27 6 26 5 25 4 24 3 23 2 22 1 21 0 20
7 27 6 26 5 25 4 24 3 23 2 22 1 21 0 20
ArrayDeque
[7, 6, 5, 4, 3, 2, 1, 0, 20, 21, 22, 23, 24, 25, 26,
27]
7 27 6 26 5 25 4 24 3 23 2 22 1 21 0 20
7 27 6 26 5 25 4 24 3 23 2 22 1 21 0 20
LinkedBlockingDeque
[4, 3, 2, 1, 0, 20, 21, 22, 23, 24]
4 24 3 23 2 22 1 21 0 20
4 24 3 23 2 22 1 21 0 20
ConcurrentLinkedDeque
[7, 6, 5, 4, 3, 2, 1, 0, 20, 21, 22, 23, 24, 25, 26,
27]
7 27 6 26 5 25 4 24 3 23 2 22 1 21 0 20
7 27 6 26 5 25 4 24 3 23 2 22 1 21 0 20
*/