Class Philosopher

java.lang.Object
  |
  +--Process
        |
        +--Philosopher

All Implemented Interfaces:

java.lang.Runnable

public class Philosopher

extends Process

A Philosopher is a process that thinks and eats. When a philosopher starts to eat, it must first get its left and right chopsticks.

Field Summary

static int	EATING EATING is the state constant for eating philosophers.
static int	HUNGRY HUNGRY is the state constant for hungry philosophers.
protected Philosopher	left left is the left neighbor of this philosopher.
protected java.lang.String	leftChopstick leftChopstick is the name of the chopstick to the left of this philosopher.
protected static Semaphore	mutex mutex is a mutual exclusion semaphore that is used by all philosophers when accessing philosopher state information.
protected Semaphore	permission permission controls permission to eat for this philosopher.
protected Philosopher	right right is the right neighbor of this philosopher.
protected int	state state is the state of this philosopher: THINKING, HUNGRY, or EATING.
static int	THINKING THINKING is the state constant for thinking philosophers.

Constructor Summary

Philosopher(java.lang.String nm, double t)
new Philosopher(nm, t) returns a new philosopher and starts executing its run method in a new thread.

Method Summary

protected void	eat() eat() simulates eating for this philosopher.
java.lang.String	getLeftChopstick() phil.getLeftChopstick(p) returns the name of the chopstick to the left of phil.
static void	go() Philosopher.go() allows philosophers to access their state information.
protected void	pickUpChopsticks() pickUpChopsticks() simulates picking up chopsticks for this philosopher.
protected void	putDownChopsticks() putDownChopsticks() simulates putting down chopsticks for this philosopher.
void	setLeftNeighbor(Philosopher p) phil.setLeftNeighbor(p) makes p the left neighbor of phil and makes phil the right neighbor of p.
protected void	step() phil.step() simulates a think and eat cycle for phil.
protected void	think() think() simulates thinking for this philosopher.
protected static void	tryToGrantPermission(Philosopher p) tryToGrantPermission(p) attempts to grant permission for p to eat.

Methods inherited from class Process

run, setSimulationTime, toString, twiddle

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

THINKING

public static final int THINKING

THINKING is the state constant for thinking philosophers.

HUNGRY

public static final int HUNGRY

HUNGRY is the state constant for hungry philosophers.

EATING

public static final int EATING

EATING is the state constant for eating philosophers.

state

protected int state

state is the state of this philosopher: THINKING, HUNGRY, or EATING.

left

protected Philosopher left

left is the left neighbor of this philosopher.

right

protected Philosopher right

right is the right neighbor of this philosopher.

permission

protected Semaphore permission

permission controls permission to eat for this philosopher.

leftChopstick

protected java.lang.String leftChopstick

leftChopstick is the name of the chopstick to the left of this philosopher.

mutex

protected static Semaphore mutex

mutex is a mutual exclusion semaphore that is used by all philosophers when accessing philosopher state information. This semaphore should be initialized to 0 to keep philosophers from executing critical code before their neighbors have been set up. The go() method should be invoked after the neighbors have been set up.

Constructor Detail

Philosopher

public Philosopher(java.lang.String nm,
                   double t)

new Philosopher(nm, t) returns a new philosopher and starts executing its run method in a new thread. The name of the new philosopher is formed by concatenating its class name with nm. The average thinking or eating time for the new philosopher is t. The name of its permission semaphore is "Permission " concatenated with nm. The name of the chopstick to its left is "Chopstick " concatenated with nm. A philosopher is born in the thinking state.

Method Detail

setLeftNeighbor

public void setLeftNeighbor(Philosopher p)

phil.setLeftNeighbor(p) makes p the left neighbor of phil and makes phil the right neighbor of p.

getLeftChopstick

public java.lang.String getLeftChopstick()

phil.getLeftChopstick(p) returns the name of the chopstick to the left of phil.

step

protected void step()

phil.step() simulates a think and eat cycle for phil.

Overrides:

step in class Process

think

protected void think()

think() simulates thinking for this philosopher.

pickUpChopsticks

protected void pickUpChopsticks()

pickUpChopsticks() simulates picking up chopsticks for this philosopher.

eat

protected void eat()

eat() simulates eating for this philosopher.

putDownChopsticks

protected void putDownChopsticks()

putDownChopsticks() simulates putting down chopsticks for this philosopher.

tryToGrantPermission

protected static void tryToGrantPermission(Philosopher p)

tryToGrantPermission(p) attempts to grant permission for p to eat. Permission is only granted if p's left and right neighbors are not eating.

go

public static void go()

Philosopher.go() allows philosophers to access their state information. This method must be invoked to start a simulation. It should not be invoked before neighbors have been set up for all philosophers.