server/Queue/Queue.java

import java.util.LinkedList;
import java.util.NoSuchElementException;

class Queue {
    
    public Queue() {
        // Possible use this method instead ?
        //_list = Collections.synchronizedList(new LinkedList(...));
        _list = new LinkedList();
    }
    
    public synchronized void add(Object o) {
        int s = _list.size();
        // add() does the same thing, but this ensures behaviour
        _list.addLast(o);
        if (s == 0) {
            notifyAll();
        }
        _count++;
    }
    
    public synchronized Object get() {
        if (_list.size() == 0) {
            try { wait(); } catch(Exception e) {}
        }
        Object o = null;
        try {
            o = _list.removeFirst();
        }
        catch (NoSuchElementException e) {
            // no element... null already... so just leave
        }
        return o;
    }
    
    public String status() {
        String status = "";
        status += "Current queue size = "+_list.size();
        status += "\n";
        status += "Queue-ometer = "+_count;
        return status;
    }
    
    private LinkedList _list;
    private int _count;
}
Revision:	1.1
Committed:	Thu Dec 28 00:58:43 2000 UTC (24 years, 10 months ago) by tdb
Branch:	MAIN
Log Message:	Starting point for a Queue that works in a multi-threaded environment. Currently no comments, no tidying, or conformity to standards, but it works :-) Further additions will include those just mentioned, plus support for a single 'producer' and multiple 'consumers', which is more precisely what we require.
#	Content
1	import java.util.LinkedList;
2	import java.util.NoSuchElementException;
3
4	class Queue {
5
6	public Queue() {
7	// Possible use this method instead ?
8	//_list = Collections.synchronizedList(new LinkedList(...));
9	_list = new LinkedList();
10	}
11
12	public synchronized void add(Object o) {
13	int s = _list.size();
14	// add() does the same thing, but this ensures behaviour
15	_list.addLast(o);
16	if (s == 0) {
17	notifyAll();
18	}
19	_count++;
20	}
21
22	public synchronized Object get() {
23	if (_list.size() == 0) {
24	try { wait(); } catch(Exception e) {}
25	}
26	Object o = null;
27	try {
28	o = _list.removeFirst();
29	}
30	catch (NoSuchElementException e) {
31	// no element... null already... so just leave
32	}
33	return o;
34	}
35
36	public String status() {
37	String status = "";
38	status += "Current queue size = "+_list.size();
39	status += "\n";
40	status += "Queue-ometer = "+_count;
41	return status;
42	}
43
44	private LinkedList _list;
45	private int _count;
46	}