dsa

Data Structures & Algorithms - Spring 2018
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StackSLS.java (1513B)

      1 package collections;
      2 
      3 public class StackSLS<T> implements StackInterface<T> {
      4 
      5     private Node<T> top;
      6    //  private int numItems;
      7 
      8     public StackSLS() {
      9         top = null;
     10     }
     11 
     12     public int size() {
     13         int size = 0;
     14         for (Node temp = top; temp != null; temp = temp.getNext()) {
     15             size++;
     16         }
     17         return size;
     18     }
     19 
     20     public boolean isEmpty() {
     21         return top == null;
     22     }
     23 
     24     public void popAll() {
     25         top = null;
     26     }
     27 
     28     public void push (T item) {
     29         top  = new Node<T>(item, top);
     30     }
     31 
     32     public T pop()
     33             throws StackException{
     34         T result;
     35         if (top == null) {
     36             throw new StackException("StackException: Stack is empty on pop");
     37         }
     38         else {
     39             result = top.getItem();
     40             top = top.getNext();
     41             return result;
     42         }
     43     }
     44 
     45     public T peek() {
     46         if (top == null) {
     47             throw new StackException("StackException: Stack is empty on peek()");
     48         }
     49         else {
     50             return top.getItem();
     51         }
     52     }
     53 
     54     @Override
     55     public String toString() {
     56         Object dataItem;
     57         Node curr = top;
     58         String result = "Stack of size " + size() + " has the following items : ";
     59         for (int i = 0; i < size(); i++) {
     60             if (curr != null) {
     61                 dataItem = curr.getItem();
     62                 curr = curr.getNext();
     63                 result += dataItem + " ";
     64             }
     65         }
     66         return result;
     67     }
     68 
     69 
     70 }