$//$ The Planting Synchronization Problem

$//$

import java.util.Random;

import java.util.concurrent.Semaphore;

public class Planting

$\{$

public static void main$($String args$[])$

$\{$

int i;

$//$ Create Student, TA$,$ Professor threads

TA ta $=$ new TA$()$;

Professor prof $=$ new Professor$($ta$)$;

Student stdnt $=$ new Student$($ta$)$;

$//$ Start the threads

prof.start$()$;

ta$.$start$()$;

stdnt$.$start$()$;

$//$ Wait for prof to call it quits

try $\{$prof$.$join$()$;$\}$ catch$($InterruptedException e$)\{\}$;

$//$ Terminate the TA and Student Threads

ta$.$interrupt$()$;

stdnt$.$interrupt$()$;

$\}$

$\}$

class Student extends Thread

$\{$

TA ta;

public Student$($TA taThread$)$

$\{$

ta $=$ taThread;

$\}$

public void run$()$

$\{$

while$($true$)$

$\{$

System.out.println$("$Student: Must wait for TA $"+$ta$.$getMAX$()+"$ holes ahead"$)$;

$//$ Can dig a hole $-$ lets get the shovel

System.out.println$("$Student: Got the shovel"$)$;

try $\{$sleep$(($int$)(100*$Math$.$random$()))$;$\}$ catch $($Exception e$)\{$ break;$\}//$ Time to fill hole

ta$.$incrHoleDug$()$; $//$ hole filled $-$ increment the number

System.out.println$("$Student: Hole $"+$ta$.$getHoleDug$()+"$ Dug"$)$;

System.out.println$("$Student: Letting go of the shovel"$)$;

if$($isInterrupted$())$ break;

$\}$

System.out.println$("$Student is done"$)$;

$\}$

$\}$

class TA extends Thread

$\{$

$//$ Some variables to count number of holes dug and filled $-$ the TA keeps track of things

private int holeFilledNum$=0$; $//$ number of the hole filled

private int holePlantedNum$=0$; $//$ number of the hole planted

private int holeDugNum$=0$; $//$ number of hole dug

private final int MAX$=5$; $//$ can only get $5$ holes ahead

$//$ add semaphores $-$ the professor lets the TA manage things.

public int getMAX$()\{$ return$($MAX$)$; $\}$

public void incrHoleDug$()\{$ holeDugNum$++$; $\}$

public int getHoleDug$()\{$ return$($holeDugNum$)$; $\}$

public void incrHolePlanted$()\{$ holePlantedNum$++$; $\}$

public int getHolePlanted$()\{$ return$($holePlantedNum$)$; $\}$

public TA$()$

$\{$

$//$ Initialise things here

$\}$

public void run$()$

$\{$

while$($true$)$

$\{$

System.out.println$("$TA: Got the shovel"$)$;

try $\{$sleep$(($int$)(100*$Math$.$random$()))$;$\}$ catch $($Exception e$)\{$ break;$\}//$ Time to fill hole

holeFilledNum$++$; $//$ hole filled $-$ increment the number

System.out.println$("$TA: The hole $"+$holeFilledNum$+"$ has been filled"$)$;

System.out.println$("$TA: Letting go of the shovel"$)$;

if$($isInterrupted$())$ break;

$\}$

System.out.println$("$TA is done"$)$;

$\}$

$\}$

class Professor extends Thread

$\{$

TA ta;

public Professor$($TA taThread$)$

$\{$

ta $=$ taThread;

$\}$

public void run$()$

$\{$

while$($ta$.$getHolePlanted

$\{$

try $\{$sleep$(($int$)(50*$Math$.$random$()))$;$\}$ catch $($Exception e$)\{$ break;$\}//$ Time to plant

ta$.$incrHolePlanted$()$; $//$ the seed is planted $-$ increment the number

System.out.println$("$Professor: All be advised that I have completed planting hole $"+$

ta$.$getHolePlanted$())$;

$\}$

System.out.println$("$Professor: We have worked enough for today"$)$;

$\}$

$\}$

$//$Code is in C