Boat.java

package nachos.threads;
import nachos.ag.BoatGrader;

public class Boat {
    static BoatGrader bg;
    static Communicator commFinish;

    static Lock incrLock, boatLock, catmLock, cawcLock, wwLock;
    static int adultsOahu, childrenOahu, adultsMolokai, childrenMolokai;
    static boolean passengerTaken;
    static Condition childrenAllToMolokai, comebackAndWakeCoordinator, waitWake;

    public static void selfTest() {
        BoatGrader b = new BoatGrader();

        System.out.println("\n ***Testing Boats with only 2 children***");
        begin(0, 2, b);

//	System.out.println("\n ***Testing Boats with 2 children, 1 adult***");
//  	begin(1, 2, b);

//  	System.out.println("\n ***Testing Boats with 3 children, 3 adults***");
//  	begin(3, 3, b);
    }

    public static void begin( int adults, int children, BoatGrader b ) {
        // Store the externally generated autograder in a class
        // variable to be accessible by children.
        bg = b;

        // Instantiate global variables here
        commFinish = new Communicator();
        incrLock = new Lock();
        boatLock = new Lock();
        catmLock = new Lock();
        childrenAllToMolokai = new Condition(catmLock);
        cawcLock = new Lock();
        comebackAndWakeCoordinator = new Condition(cawcLock);
        wwLock = new Lock();
        waitWake = new Condition(wwLock);

        adultsOahu = 0;
        adultsMolokai = 0;
        childrenOahu = 0;
        childrenMolokai = 0;
        passengerTaken = false;

        // Create threads here. See section 3.4 of the Nachos for Java
        // Walkthrough linked from the projects page.

        for(int i = 0; i < adults; i++) {
            KThread t = new KThread(new Runnable() {
                @Override
                public void run() {
                    AdultItinerary();
                }
            });
            t.setName("Adult #" + i);
            t.fork();
        }
        for(int i = 0; i < children; i++) {
            KThread t = new KThread(new Runnable() {
                @Override
                public void run() {
                    ChildItinerary();
                }
            });
            t.setName("Child #" + i);
            t.fork();
        }

        commFinish.listen();
        bg.AllCrossed();
    }

    static void AdultItinerary() {
        bg.initializeAdult(); //Required for autograder interface. Must be the first thing called.
        //DO NOT PUT ANYTHING ABOVE THIS LINE.

        /* This is where you should put your solutions. Make calls
           to the BoatGrader to show that it is synchronized. For
           example:
               bg.AdultRowToMolokai();
           indicates that an adult has rowed the boat across to Molokai
        */
        incrLock.acquire();
        adultsOahu++;
        incrLock.release();

        catmLock.acquire();
        childrenAllToMolokai.sleep();
        catmLock.release();
        bg.AdultRowToMolokai();
        adultsOahu--;
        cawcLock.acquire();
        comebackAndWakeCoordinator.wake();
        cawcLock.release();
    }

    static void ChildItinerary() {
        bg.initializeChild(); //Required for autograder interface. Must be the first thing called.
        //DO NOT PUT ANYTHING ABOVE THIS LINE.
        incrLock.acquire();
        childrenOahu++;
        incrLock.release();

        ThreadedKernel.alarm.waitUntil(500);

        while(true) {
            boatLock.acquire();
            if(!passengerTaken && childrenOahu > 0) {
                passengerTaken = true;
                bg.ChildRideToMolokai();
                childrenOahu--;
                childrenMolokai++;
                boatLock.release();

                while(true) {
                    cawcLock.acquire();
                    comebackAndWakeCoordinator.sleep();
                    cawcLock.release();
                    bg.ChildRowToOahu();
                    wwLock.acquire();
                    waitWake.wake();
                    wwLock.release();
                    bg.ChildRideToMolokai();
                }
            } else {
                passengerTaken = false;
                bg.ChildRowToMolokai();
                childrenOahu--;
                childrenMolokai++;
                if(childrenOahu > 0) {
                    bg.ChildRowToOahu();
                    childrenMolokai--;
                    childrenOahu++;
                    boatLock.release();
                } else {
                    // begin coordinating
                    bg.ChildRowToOahu();
                    childrenMolokai--;
                    childrenOahu++;
                    while(adultsOahu > 0) {
                        catmLock.acquire();
                        childrenAllToMolokai.wake();
                        catmLock.release();
                        wwLock.acquire();
                        waitWake.sleep();
                        wwLock.release();
                        bg.ChildRowToMolokai();
                        bg.ChildRowToOahu();
                    }
                    bg.ChildRowToMolokai();
                    childrenMolokai++;
                    childrenOahu--;
                    commFinish.speak(1);
                    return ;
                }
            }
        }
    }

}