Java ArrayDeque contains方法

package com.codingdict;

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

public class ArrayDequeDemo {
   public static void main(String[] args) {

      // create an empty array deque with an initial capacity
      Deque<Integer> deque = new ArrayDeque<Integer>(8);

      // use add() method to add elements in the deque
      deque.add(20);
      deque.add(30);
      deque.add(10);
      deque.add(18);        

      // let us print all the elements available in deque
      for (Integer number : deque) {
         System.out.println("Number = " + number);
      }

      // deque contains element 10
      boolean retval = deque.contains(10);

      if (retval == true) {
         System.out.println("element 10 is contained in the deque");
      } else {
         System.out.println("element 10 is not contained in the deque");
      }

      // deque does not contain element 25
      boolean retval2 = deque.contains(25);

      if (retval2 == true) {
         System.out.println("element 25 is contained in the deque");
      } else {
         System.out.println("element 25 is not contained in the deque");    
      }
   }
}