Generic Queue - Java Data Structure

Java examples for Data Structure:queue

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Description

Generic Queue

Demo Code

public class GenericQueue<Item> {
    private Node<Item> first;
    private Node<Item> last;

    public Item dequeue() {
        if (first == null) {
            throw new java.lang.IndexOutOfBoundsException();
        }//w  ww. jav a  2  s .  c  o  m
        Item firstval = first.item;
        // check if this is the last item
        if (first.next == null) {
            first = null;
            last = null;
        } else
            first = first.next;
        return firstval;
    }

    public void enqueue(Item s) {
        Node<Item> newlast = new Node<Item>();
        newlast.item = s;
        newlast.next = null;
        if (first == null)
            first = newlast;
        else
            last.next = newlast;
        last = newlast;
    }

    public static void main(String[] args) {
        GenericQueue<Integer> queue = new GenericQueue<Integer>();
        while (!StdIn.isEmpty()) {
            String s = StdIn.readString();
            //StdOut.print(s);
            if (s.equals("-"))
                System.out.println(queue.dequeue());
            else
                queue.enqueue(Integer.parseInt(s));
        }
    }

    private class Node<Item> {
        Item item;
        Node<Item> next;
    }
}

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