FIFO class in Java

问题:

I want to implement FIFO through a class in Java.

Does such a class already exist? If not, how can I implement my own?

NOTE

I found a class here http://www.dcache.org/manuals/cells/docs/api/dmg/util/Fifo.html, but it doesn't contain dmg.util.*. I don't know if such a package even exists.

回答1:

You're looking for any class that implements the Queue interface, excluding PriorityQueue and PriorityBlockingQueue, which do not use a FIFO algorithm.

Probably a LinkedList using add (adds one to the end) and removeFirst (removes one from the front and returns it) is the easiest one to use.

For example, here's a program that uses a LinkedList to queue and retrieve the digits of PI:

import java.util.LinkedList;

class Test {
    public static void main(String args[]) {
        char arr[] = {3,1,4,1,5,9,2,6,5,3,5,8,9};
        LinkedList<Integer> fifo = new LinkedList<Integer>();

        for (int i = 0; i < arr.length; i++)
            fifo.add (new Integer (arr[i]));

        System.out.print (fifo.removeFirst() + ".");
        while (! fifo.isEmpty())
            System.out.print (fifo.removeFirst());
        System.out.println();
    }
} 

---

Alternatively, if you know you only want to treat it as a queue (without the extra features of a linked list), you can just use the Queue interface itself:

import java.util.LinkedList;
import java.util.Queue;

class Test {
    public static void main(String args[]) {
        char arr[] = {3,1,4,1,5,9,2,6,5,3,5,8,9};
        Queue<Integer> fifo = new LinkedList<Integer>();

        for (int i = 0; i < arr.length; i++)
            fifo.add (new Integer (arr[i]));

        System.out.print (fifo.remove() + ".");
        while (! fifo.isEmpty())
            System.out.print (fifo.remove());
        System.out.println();
    }
}

This has the advantage of allowing you to replace the underlying concrete class with any class that provides the Queue interface, without having to change the code too much.

The basic changes are to change the type of fifo to a Queue and to use remove() instead of removeFirst(), the latter being unavailable for the Queue interface.

Calling isEmpty() is still okay since that belongs to the Collection interface of which Queue is a derivative.

回答2:

Try ArrayDeque or LinkedList, which both implement the Queue interface.

http://docs.oracle.com/javase/6/docs/api/java/util/ArrayDeque.html

回答3:

Queues are First In First Out structures. You request is pretty vague, but I am guessing that you need only the basic functionality which usually comes out with Queue structures. You can take a look at how you can implement it here.

With regards to your missing package, it is most likely because you will need to either download or create the package yourself by following that tutorial.

回答4:

You don't have to implement your own FIFO Queue, just look at the interface java.util.Queue and its implementations

回答5:

if you want to have a pipe to write/read data, you can use the http://docs.oracle.com/javase/6/docs/api/java/io/PipedWriter.html

回答6:

You can use LinkedBlockingQueue I use it in my projects. It's part of standard java and quite easy to use