Issues with imports/library?

Question

I am working on an assignment for class:

Josephus problem. In the Josephus problem from antiquity, N people are in dire straits and agree to the following strategy to reduce the population. They arrange themselves in a circle (at positions numbered from 0 to N???1) and proceed around the circle, eliminating every Mth person until only one person is left. Legend has it that Josephus figured out where to sit to avoid being eliminated. Write a Queue client Josephus.java that takes M and N from the command line and prints out the order in which people are eliminated (and thus would show Josephus where to sit in the circle).

My code is as follows :

package josephus; 
import java.util.Queue;

public class Josephus  { 

public static void main(String[] args)  {
    int n = Integer.parseInt(args[0]),
        m = Integer.parseInt(args[1]);

    Queue<Integer> q = new Queue<Integer>();
    for (int i = 0; i < n; i++)
        q.enqueue(new Integer(i));

    int k = 0;
    while (!q.isEmpty())
    {
        int x = q.dequeue();

        if (++k % m == 0)
            StdOut.print(x + " ");
        else
            q.enqueue(x);
    }
    StdOut.println();
} }

When I run it in NetBeans it gives me errors stating that:

Queue is abstract; cannot be instantiated

enqueue: Cannot find symbol

dequeue: Cannot find symbol

StdOut: Cannot find symbol

I thought that by importing the java.util.Queue would make the Queue work and for the StdOut I did download a stdlib.jar to add to the projects library which inculdes StdOut and I thought that would work.

If there is a problem with my code or anything else I need to do, I would really appreciate the help. Also, for reference and to see where I got the stdlib.jar, here is the link for the textbooks website from where this problem comes from : http://algs4.cs.princeton.edu/13stacks/ (The Josephus problem is #37 under the "Creative problems section" towards the end.

possible duplicate of [How do I instantiate a Queue object in java?](http://stackoverflow.com/questions/4626812/how-do-i-instantiate-a-queue-object-in-java) — DavidPostill, Sep 04 '14 at 21:22
Queue q = new LinkedList(); the problem with your code is that you are trying to instantiate an interface. — coffeeaddict, Sep 04 '14 at 21:23
Use [public void println(String x)](http://docs.oracle.com/javase/7/docs/api/java/io/PrintStream.html#println%28java.lang.String%29) for printing — DavidPostill, Sep 04 '14 at 21:26
You may also want to read up on Queues in the Java documentation -- here is the link http://docs.oracle.com/javase/tutorial/collections/interfaces/queue.html — ErstwhileIII, Sep 04 '14 at 22:09

score 0 · Accepted Answer · answered Sep 04 '14 at 21:24

0

Queue is an interface and cannot be directly instantiated in Java. You must provide a concrete implementation class, such as ArrayDeque.

Queue<Integer> q = new ArrayDeque<Integer>();

The queue methods enqueue and dequeue are named differently -- offer and poll, respectively. E.g.:

q.offer(i);

and

int x = q.poll();

StdOut is not a class in Java; use System.out, e.g.:

System.out.print(x + " ");

answered Sep 04 '14 at 21:24

rgettman

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Thank you @rgettman. I tried your suggestion and it worked out! – Christophorus Sep 14 '14 at 09:22

Issues with imports/library?

1 Answers1