Java Stacks -Write a generic collection for a Stack using Node UML for Stack Sta

Question

Java
Stacks
-Write a generic collection for a Stack using Node

UML for Stack
Stack
-top : Node
-numElements : int
+Stack( )
+push( element : E ) : void
+pop( ) : E
+size( ) : int

private fields:
- top which points to a Node
- numElements an int
a no-arg Constructor +Stack( ) :
- sets top to null
- numElements to 0
push(receives element of type E)
- adds a new node to top of stack
- adds 1 to numElements
pop( ) returns a value of type E
- removes node from top of stack
- decrements numElements by 1
- <<unless stack="" is="" empty="" then="" return="" null="" and="" don't="" decrement="" numelements="">>
size( ) returns an int
- returns value of numElements

Explanation / Answer

Driver.java
public class Driver{
    public static void main(String[]args){
   String s;
   Queue n = new Queue();
   System.out.println(n);
   n.nQ("first");
   System.out.println(n);
   n.nQ("second");
   System.out.println(n);
   n.nQ("third");
   System.out.println(n);
   s = n.dQ();
   System.out.println(s + "   |   " + n);
   s = n.dQ();
   System.out.println(s + "   |   " + n);
   s = n.dQ();
   System.out.println(s + "   |   " + n);
   s = n.dQ();
   System.out.println(s + "   |   " + n);
    }
}

Node.java
public class Node{
    private String data;
    private Node next;
  
    public Node(String s){
   data = s;
   next = null;

    }

    public void setData(String s){
   data = s;

    }

    public String getData(){
   return data;
    }

    public void setNext(Node n){
   next = n;
    }

    public Node getNext(){
   return next;
    }

    public String toString(){
   return ""+ data;
    }

}

Queue.java
public class Queue{
  
    private Node head;
    private Node tail;
    private int length;

    public Queue(){
   head = null;
   tail = null;
   length = 0;
    }

    public void nQ(String s){
   Node n = new Node(s);
   if (length == 0){
        head = n;
        tail = n;
   }
   else {
        tail.setNext(n);
        tail = n;
   }
   length++;
    }

    public String dQ(){
   String s;
   if (head == null){
        return null;
   }
   s = head.getData();
   head = head.getNext();
   length--;
   if (head == null){
        tail = null;
   }
   return s;
    }

    public String front(){
   return head.getData();
    }
  
    public int size(){
   return length;
    }

    public String toString(){
   String s = "Head --> ";
   if (head == null){
        s = s + "null -->";
   }
   Node temp = head;
   while (temp != null){
        s = s + temp.getData() + " --> ";
        temp = temp.getNext();
   }
   s = s.substring(0, s.length() - 4);
   s = s + " <-- tail";
   return s;
    }
  
  
}

arrayQueue.java
public class arrayQueue{
  
    private String[10] q;
    private String head,tail;
    private int size;

    public arrayQueue(){
   head = "";
   tail = "";
    }

    public void nQ(String s){
   if (size == 0){
        q[size] = s;
        head = s;
        tail = s;
   }
   if (size < 10 && size > 0){
        q[size + 1] = s;
        tail = q[size + 1];
   }
   else{
        return;
   }
    }

    public String dQ(){
   String s;
   s = head;
   for (int i = 0; i < size; i++){
        q[i] = q[i + 1];
   }
   return s;
    }

    public String front(){
   return head;
    }
}

sample output

Head --> null <-- tail                                                                                                                                      
Head --> first <-- tail                                                                                                                                    
Head --> first --> second <-- tail                                                                                                                         
Head --> first --> second --> third <-- tail                                                                                                               
first   |   Head --> second --> third <-- tail                                                                                                             
second   |   Head --> third <-- tail                                                                                                                       
third   |   Head --> null <-- tail                                                                                                                          
null   |   Head --> null <-- tail                                                                                                                           

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