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

SimpleLinkedList.java

/* Simple Linked List with Insert First */
class SimpleLinkedList  {
  private Node first; // private link to the first element
  
  // constructor sets first to null
  public void SimpleLinkedList(){
    this.first = null;
  } 
  
  public boolean isEmpty(){
    if (this.first == null) {
      return true;
    } else {
      return false;
    }
  } // returns true if list is empty
  
  // Added this method to insert a node to the beginning
  public void insertFirst(int i) {    //accept new values
    Node newNode = new Node(i);       // create a new link
    newNode.next = first;             // change the new link’s next reference
    first = newNode;                  // Change first to reference the new link, where index = 0
  }
  
  public Node deleteFirst() {
    Node temp = first;       // reset the first reference to first.next
    first = first.next;      // reroute downstream
    return temp;             // return deleted link
  }
}

Stack.java

class Stack {
  private LinkList theList;

  public LinkStack() {            // constructor
    theList = new LinkList();
  }

  public void push(int i) {    // put item on top of stack
    theList.insertFirst(i);
  }

  public long pop() {           // take item from top of stack    
    return theList.deleteFirst();
  }

  public boolean isEmpty() {      // true if stack is empty
    return ( theList.isEmpty() );
  }

  public void displayStack() {
    System.out.print("Stack (top-->bottom): ");
    theList.displayList();
  }

}  // end class LinkStack