Chapter 9:  "Stacks and Queues"

Data Structures with Java, Rick Mercer

Answers to Self-Check Questions


 9-1  z
      y
      x
       
 9-2 true
     <<<
     
 9-3 false
     1
     2
     3
     true
     

 9-4 Check symbols in Test2.java
     Abc.java:2 expecting ]
     Abc.java:4 expecting }
     Abc.java:4 expecting }
     missing }
     4 errors
     
 9-5 Java

 9-6 first
     first
     first 
       ...
     first until someone terminates the program or the power goes out 
     
 9-7 // OurQueue does not implement Iterable so the enhanced for loop can not be used
     int size = intQueue.size();
     for (int j = 1; j <= size; j++) {
         int nextInt = intQueue.peek();
         if (nextInt % 2 != 0)
             System.out.println(nextInt + " is odd");
         else
             System.out.println(nextInt + " is even");
         intQueue.remove();
         intQueue.add(nextInt);
     }
        
     
 9-8  front o-> |5.6|o->|7.8|<-o back
 
 9-9  front o-> |"a"|o->|"7.8"|<-o back
 
9-10  @Override
      public String toString() {
          String result = "[";
 
          // Concatenate all but the last one (if size > 0)
          Node ref = front;
          while (ref != back) {
              result += ref.data + ", ";
              ref = ref.next;
          }
    
          // Last element does not have ", " after it
          if (ref != null)
              result += ref.data;
  
          result += "]";
  
          return result;
     }


9-11 public E remove() throws NoSuchElementException {
        if (this.isEmpty())
            throw new NoSuchElementException();

        E frontElement = front.data;
        front = front.next;

        if (front == null)
            front = back = null;

        return frontElement;
     }