CISC 3130 Spring 2020 OER Code Snippets for https://libguides.brooklyn.cuny.edu/cisc3130/

DoubleEndedLinkedList.java

/* Double-ended Linked List with Insert First, Insert Last */

class DoubleEndedLinkedList  {
  private Node first; // private link to the first element
  private Node last;
  
  // constructor sets first to null
  public void DoubleEndedLinkedList(){
    this.first = null;
    this.last = null;
  } 
  
  public boolean isEmpty(){
    return first == null;             // returns true if list is empty
  }

  // Added this method to insert a node to the end
  public void insertLast(int i){
    Node newNode = new Node(i); 
    if( isEmpty() )                // if empty list,
      first = newNode;             // first --> newNode
    else
      last.next = newNode;         // old last --> newNode
    
    last = newNode;                // newNode <-- last
  }
  
  public Node deleteFirst() {
    Node temp = first;        // reset the first reference to first.next
    if(first.next == null)    // if only one item
       last = null;           // null <-- last
    first = first.next;       // first --> old next
    return temp;              // return deleted link
  }
}

LinkQueue.java

class LinkQueue {
  private DoubleEndedLinkedList theList;

  public LinkQueue() {               // constructor
    theList = new FirstLastList();   // make a nelist
  }
  
  public boolean isEmpty() {         // true if queue is empty
    return theList.isEmpty();
  }

  public void insert(int i) {        // insert, rear of queue
    theList.insertLast(j);
  }

  public int remove() {              // remove, front of queue
    return theList.deleteFirst();
  }
  
  public void displayQueue() {
      System.out.print("Queue (front-->rear): ");
      theList.displayList();
  }
} // end LinkQueue