source: liacs/cvp/java/first/Database.java@ 50

/*
 * Rick van der Zwet
 * 0433373
 * Java programming assigment 1.2
 * Licence: BSD
 * $Id: Database.java 270 2007-10-13 13:45:29Z rick $
 */

class Database
{
// Read lock, call next person
// Write lock, call next person when done
    private int readlock = 0;
    private boolean  writelock = false;

    private String value = new String("INIT");

    Database () {}; // constructor

    synchronized void get_readlock ()
    {
        while (writelock)
        {
            try { wait(); } catch (InterruptedException e)
            {
                System.out.println("interruptedException caught");
            }
        }
        readlock++;
    }

    synchronized String read ()
    {
        return (value);
    }

    synchronized void release_readlock ()
    {
        readlock--;
        notify();
    }

    synchronized void get_writelock()
    {
        while (writelock && readlock > 0)
        {
            try { wait(); } catch (InterruptedException e)
            {
                System.out.println("interruptedException caught");
            }
        }
        writelock = true;
    }

    synchronized void write (String text)
    {
        value = value + ":" + text;
    }

    synchronized void release_writelock()
    {
        writelock = false;
        notify();
    }
}