A single-lane bridge connects village A to village B. Farmers in the two villages use this bridge to deliver their products to the neighboring town. The bridge can become deadlocked if a farmer from village A and a farmer from village B get on the bridge at the same time. Using semaphores and/or mutex locks (do not be concerned about starvation) implement your solution in Java. In particular, represent village A and village B farmers as separate threads. Once a farmer is on the bridge, the associated thread will sleep for a random period of time, representing traveling across the bridge.

Main Java

Explanation:

code:

Main.java

import java.lang.InterruptedException;

import java.lang.Thread;

import java.util.Random;

public class Main {

   final private static int FARMERS = 10;

   public static void main(String[] args) {

       Bridge bridge = new Bridge();

       Random r = new Random();

       System.out.println("Running with " + FARMERS + " farmers...");

       // Enter a bunch of farmers from different directions.

       for (int i = 0; i < FARMERS; i++) {

           Farmer farmer;

           if (r.nextBoolean()) {

               farmer = new SouthBoundFarmer(bridge);

           } else {

               farmer = new NorthBoundFarmer(bridge);

           }

           cross(farmer);

       }

   }

   private static void cross(Farmer f) {

       new Thread(f).start();

   }

}

SouthBoundFarmer.java

public class SouthBoundFarmer extends Farmer {

   public SouthBoundFarmer(Bridge b) {

       super(b);

       this.name = "South";

   }

}

Farmer.java

import java.lang.InterruptedException;

import java.util.Random;

public class Farmer implements Runnable {

   private Bridge bridge;

   private Random random;

   protected String name;

   public Farmer(Bridge b) {

       this.bridge = b;

       this.random = new Random();

   }

   public void crossBridge(Bridge bridge) {

       System.out.println("[" + this.name + "] Waiting to enter bridge...");

       try {

           bridge.enter();

           System.out.println("[" + this.name + "] Entering bridge...");

           // Crossing bridge...some farmers are fast, others are slow :P

           Thread.sleep(1000 + random.nextInt(9000));

           System.out.println("[" + this.name + "] Leaving bridge...");

       } catch (InterruptedException e) {

           System.out.println("...Interrupted!");

       } finally {

           bridge.leave();

       }

   }

   public void run() {

       this.crossBridge(this.bridge);

   }

}

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