queue programming in Java does not update the queue

Question

I want to program a enqueue(elem) in Java, so I have programmed the following modules:

public class Node{
    public int e;
    Node next;
    public Node(int e){
        this.e=e;
    }
}

and now I want to use a Linked List to store my elements, so I made a class with a enqueue() function like this:

 public class Queue{
        Node q;        //represents a queue 
        Node first;
         public void enqueue(int n){
            Node t=new Node(n);  //represents a temporal node
            if(q==null){
                first=t;
            }
            else{
                t.next=first;
                t=first;
            }
            q=t;  //to store the node into the queue
        }
}

but when I want to print the elements of my queue:

 public void print(){
            Node current=first;
            while (current!=null){
                System.out.println(current.e);
                current=current.next;
            }
        }

it only prints me the first element that I enter, for example if I put 10,20,30,40 it only prints 10. What am I doing wrong?

Thanks

I don't see how your print routine works. How are you updating current? And next isn't being used. — WJS
– WJS, Commented May 26, 2019 at 16:17
the first thing you are doing wrong is unclear identifiers. Is "q" "lastNode"? Is "t" "newLastNode"? — Alexei Kaigorodov
– Alexei Kaigorodov, Commented May 26, 2019 at 16:26
@michalk not really, q represents my queue in the form of a linked list — Little
– Little, Commented May 26, 2019 at 18:39
@AlexeiKaigorodov, thanks for pinpointing those errors I made when translating my code; now I have fixed them — Little
– Little, Commented May 26, 2019 at 18:40

arunsrajan · Accepted Answer · 2019-05-26 16:43:39Z

1

Your code for the class Queue should be the below. The node first will be the first element and q will be the last element.

public class Queue{
    Node q;
    Node first;
     public void enqueue(int n){
        Node t=new Node(n);
        if(q==null){
            first=t;
        }
        else{
            q.next=t;
        }
        q=t;
    }
     public void print(){
         Node current=first;
         while (current!=null){
             System.out.println(current.e);
             current = current.next;
         }
     }
}

answered May 26, 2019 at 16:43

arunsrajan

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