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/* The Computer Language Shootout
http://shootout.alioth.debian.org/
contributed by Keenan Tims
modified by Michael Barker
*/
public class chameneos {
private MeetingPlace mp;
public static final Colour[] COLOURS = { Colour.BLUE, Colour.RED, Colour.YELLOW, Colour.BLUE };
private Creature[] creatures = new Creature[COLOURS.length];
public enum Colour {
RED, BLUE, YELLOW, FADED
}
public class Creature extends Thread {
private MeetingPlace mp;
private Colour colour;
private int met = 0;
private Colour other;
public Creature(Colour c, MeetingPlace mp) {
this.colour = c;
this.mp = mp;
}
public void run() {
try {
while (colour != Colour.FADED) {
mp.meet(this);
if (other == Colour.FADED)
colour = Colour.FADED;
else {
met++;
colour = complement(other);
}
}
} catch (InterruptedException e) {
// Let the thread exit.
}
}
private Colour complement(Colour other) {
if (colour == other)
return colour;
switch (colour) {
case BLUE:
return other == Colour.RED ? Colour.YELLOW : Colour.RED;
case RED:
return other == Colour.BLUE ? Colour.YELLOW : Colour.BLUE;
case YELLOW:
return other == Colour.BLUE ? Colour.RED : Colour.BLUE;
default:
return colour;
}
}
public int getCreaturesMet() {
return met;
}
public Colour getColour() {
return colour;
}
public void setOther(Colour other) throws InterruptedException {
this.other = other;
}
}
public class MeetingPlace {
int n;
public MeetingPlace(int n) {
this.n = n;
}
Creature other = null;
public void meet(Creature c) throws InterruptedException {
synchronized (this) {
if (n > 0) {
if (other == null) {
other = c;
this.wait();
} else {
other.setOther(c.getColour());
c.setOther(other.getColour());
other = null;
n--;
this.notify();
}
} else {
c.setOther(Colour.FADED);
}
}
}
}
public chameneos(int n) throws InterruptedException {
int meetings = 0;
mp = new MeetingPlace(n);
for (int i = 0; i < COLOURS.length; i++) {
creatures[i] = new Creature(COLOURS[i], mp);
creatures[i].start();
}
// wait for all threads to complete
for (int i = 0; i < COLOURS.length; i++)
creatures[i].join();
// sum all the meetings
for (int i = 0; i < COLOURS.length; i++) {
meetings += creatures[i].getCreaturesMet();
}
System.out.println(meetings);
}
public static void main(String[] args) throws Exception {
if (args.length < 1)
throw new IllegalArgumentException();
new chameneos(Integer.parseInt(args[0]));
}
}
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