I am writing a program for Bully Algorithm in Java Here is the code:

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Asked: June 2, 20262026-06-02T08:44:21+00:00 2026-06-02T08:44:21+00:00

I am writing a program for Bully Algorithm in Java Here is the code:

0

I am writing a program for Bully Algorithm in Java
Here is the code:

package newbully;

public class NewBully {

    public static void main(String[] args) {
        int total_processes = 6;
        RunningThread[] t = new RunningThread[total_processes];
        for (int i = 0; i < total_processes; i++) {
            t[i] = new RunningThread(new Process(i+1, i+1), total_processes);//passing process id, priority, total no. of processes to running thread
        }
        try {
            Election.initialElection(t);
        } catch (Exception e) {
            System.out.println("Possibly you are using null references in array");
        }
        for (int i = 0; i < total_processes; i++) {
            new Thread(t[i]).start();//start every thread
        }
    }
}


package newbully;

import java.util.*;
import java.io.*;
import java.net.*;

public class RunningThread implements Runnable {

    private Process process;
    private int total_processes;
    ServerSocket[] sock;
    Random r;

    public Process getProcess() {
        return process;
    }

    public void setProcess(Process process) {
        this.process = process;
    }

    public RunningThread(Process process, int total_processes) {
        this.process = process;
        this.total_processes = total_processes;
        this.r = new Random();
        this.sock = new ServerSocket[total_processes];
    }

    synchronized private void recovery() {
        System.out.println("Process[" + this.process.getPid() + "]: -> Recovered from Crash");
        //Find current co-ordinator.
    }

    synchronized private void pingCoOrdinator() {
        try {
            if (Election.isPingFlag()) {
                synchronized (Election.lock) {
                    Election.lock.wait();
                }
            }
            if (!Election.isElectionFlag()) {
                Election.setPingFlag(true);
                System.out.println("Process[" + this.process.getPid() + "]: Are you alive?");
                Socket outgoing = new Socket(InetAddress.getLocalHost(), 12345);
                outgoing.close();
                Election.setPingFlag(false);
                synchronized (Election.lock) {
                    Election.lock.notifyAll();
                }
            }
        } catch (Exception ex) {
            //Initiate Election
            System.out.println("process[" + this.process.getPid() + "]: -> Co-Ordinator is down\nInitiating Election");
            Election.setElectionFlag(true);
            Election.setPingFlag(false);
            synchronized (Election.lock) {
                Election.lock.notifyAll();
            }
        }
    }

    synchronized private void executeJob() {
        int temp = r.nextInt(20);
        for (int i = 0; i <= temp; i++) {
            try {
                Thread.sleep(700);
            } catch (InterruptedException e) {
                System.out.println("Error Executing Thread:" + process.getPid());
                System.out.println(e.getMessage());
            }
        }
    }

    synchronized private boolean sendMessage() {
        boolean response = false;
        int i = 0;
        try {
            if (Election.isMessageFlag()) {
                synchronized (Election.lock) {
                    Election.lock.wait();
                }
            }
            Election.setMessageFlag(true);
            if (Election.isElectionFlag()) {
                for (i = this.process.getPid() + 1; i <= this.total_processes; i++) {
                    try {
                        Socket electionMessage = new Socket(InetAddress.getLocalHost(), 10000 + i);
                        System.out.println("Process[" + this.process.getPid() + "] -> Process[" + i + "]  responded to election message successfully");
                        electionMessage.close();
                        response = true;
                    } catch (Exception ex) {
                        System.out.println("Process[" + this.process.getPid() + "] -> Process[" + i + "] did not respond to election message");
                    }
                }
            }
            Election.setMessageFlag(false);
            synchronized (Election.lock) {
                Election.lock.notifyAll();
            }
        } catch (Exception ex1) {
            System.out.println(ex1.getMessage());
        }

        return response;
    }

    synchronized private void serve() {
        try {
            //service counter
            Socket incoming = null;
            ServerSocket s = new ServerSocket(12345);
            for (int counter = 0; counter < 10; counter++) {
                incoming = s.accept();
                System.out.println("Process[" + this.process.getPid() + "]:Yes");
                Scanner scan = new Scanner(incoming.getInputStream());
                PrintWriter out = new PrintWriter(incoming.getOutputStream(), true);
                if (scan.hasNextLine()) {
                    if (scan.nextLine().equals("Who is the co-ordinator?")) {
                        System.out.print("Process[" + this.process.getPid() + "]:");
                        out.println(this.process);
                    }
                }
            }
            //after serving 10 requests go down for random time
            this.process.setCoOrdinatorFlag(false);
            this.process.setDownflag(true);
            try {
                incoming.close();
                s.close();
                sock[this.process.getPid() - 1].close();
                Thread.sleep((this.r.nextInt(10) + 1) * 1000000);//going down
                recovery();
            } catch (InterruptedException e) {
                System.out.println(e.getMessage());
            }


        } catch (IOException ex) {
            System.out.println(ex.getMessage());
        }
    }

    @Override
    public void run() {
        try {
            sock[this.process.getPid() - 1] = new ServerSocket(10000 + this.process.getPid());
        } catch (IOException ex) {
            System.out.println(ex.getMessage());
        }
        while (true) {
            if (process.isCoOrdinatorFlag()) {
                //serve other processes
                serve();
            } else {
                while (true) {
                    //Execute some task
                    executeJob();

                    //Ping the co-ordinator
                    pingCoOrdinator();

                    if (Election.isElectionFlag()) {
                        if (!sendMessage()) {//elect self as co-ordinator
                            System.out.println("New Co-Ordinator: Process[" + this.process.getPid() + "]");
                            this.process.setCoOrdinatorFlag(true);
                            Election.setElectionFlag(false);
                            break;
                        }
                    }
                }
            }
        }
    }
}

package newbully;

public class Election {

    private static boolean pingFlag = false;
    private static boolean electionFlag = false;
    private static boolean messageFlag = false;
    public static final Object lock = new Object(); 

    public static boolean isMessageFlag() {
        return messageFlag;
    }

    public static void setMessageFlag(boolean messageFlag) {
        Election.messageFlag = messageFlag;
    }

    public static boolean isPingFlag() {
        return pingFlag;
    }

    public static void setPingFlag(boolean pingFlag) {
        Election.pingFlag = pingFlag;
    }

    public static boolean isElectionFlag() {
        return electionFlag;
    }

    public static void setElectionFlag(boolean electionFlag) {
        Election.electionFlag = electionFlag;
    }

    public static void initialElection(RunningThread[] t) {
        Process temp = new Process(-1, -1);
        for (int i = 0; i < t.length; i++) {
            if (temp.getPriority() < t[i].getProcess().getPriority()) {
                temp = t[i].getProcess();
            }
        }
        t[temp.pid - 1].getProcess().CoOrdinatorFlag = true;
    }
}

package newbully;

public class Process {

    int pid;
    boolean downflag,CoOrdinatorFlag;

    public boolean isCoOrdinatorFlag() {
        return CoOrdinatorFlag;
    }

    public void setCoOrdinatorFlag(boolean isCoOrdinator) {
        this.CoOrdinatorFlag = isCoOrdinator;
    }
    int priority;

    public boolean isDownflag() {
        return downflag;
    }

    public void setDownflag(boolean downflag) {
        this.downflag = downflag;
    }

    public int getPid() {
        return pid;
    }

    public void setPid(int pid) {
        this.pid = pid;
    }

    public int getPriority() {
        return priority;
    }

    public void setPriority(int priority) {
        this.priority = priority;
    }

    public Process() {
    }

    public Process(int pid, int priority) {
        this.pid = pid;
        this.downflag = false;
        this.priority = priority;
        this.CoOrdinatorFlag = false;
    }
}

Here is the output:

//--When delay in executeJob() method is 100

Process[4]: Are you alive?
Process[6]:Yes
Process[4]: Are you alive?
Process[6]:Yes
Process[3]: Are you alive?
Process[6]:Yes
Process[5]: Are you alive?
Process[6]:Yes
Process[1]: Are you alive?
Process[6]:Yes
Process[4]: Are you alive?
Process[6]:Yes
Process[3]: Are you alive?
Process[6]:Yes
Process[3]: Are you alive?
Process[6]:Yes
Process[2]: Are you alive?
Process[6]:Yes
Process[5]: Are you alive?
Process[6]:Yes
Process[1]: Are you alive?
process[1]: -> Co-Ordinator is down
Initiating Election
Process[1] -> Process[2]  responded to election message successfully
Process[1] -> Process[3]  responded to election message successfully
Process[1] -> Process[4]  responded to election message successfully
Process[1] -> Process[5]  responded to election message successfully
Process[1] -> Process[6] did not respond to election message
Process[2] -> Process[3]  responded to election message successfully
Process[3] -> Process[4]  responded to election message successfully
Process[4] -> Process[5]  responded to election message successfully
Process[2] -> Process[4]  responded to election message successfully
Process[2] -> Process[5]  responded to election message successfully
Process[3] -> Process[5]  responded to election message successfully
Process[5] -> Process[6] did not respond to election message
New Co-Ordinator: Process[5]
New Co-Ordinator: Process[1]
Address already in use: JVM_Bind
Address already in use: JVM_Bind
Address already in use: JVM_Bind


 //--When delay in executeJob() method is 700
Process[3]: Are you alive?
Process[6]:Yes
Process[5]: Are you alive?
Process[6]:Yes
Process[2]: Are you alive?
Process[1]: Are you alive?
Process[6]:Yes
Process[6]:Yes
Process[5]: Are you alive?
Process[1]: Are you alive?
Process[6]:Yes
Process[6]:Yes
Process[4]: Are you alive?
Process[6]:Yes
Process[3]: Are you alive?
Process[6]:Yes
Process[2]: Are you alive?
Process[6]:Yes
Process[1]: Are you alive?
Process[6]:Yes
Process[4]: Are you alive?
process[4]: -> Co-Ordinator is down
Initiating Election
Process[4] -> Process[5]  responded to election message successfully
Process[4] -> Process[6] did not respond to election message
Process[5] -> Process[6] did not respond to election message
New Co-Ordinator: Process[5]
Process[1]: Are you alive?
Process[5]:Yes
Process[1]: Are you alive?
Process[5]:Yes
Process[3]: Are you alive?
Process[5]:Yes
Process[2]: Are you alive?
Process[5]:Yes
Process[1]: Are you alive?
Process[5]:Yes
Process[4]: Are you alive?
Process[5]:Yes
Process[2]: Are you alive?
Process[5]:Yes
Process[4]: Are you alive?
Process[5]:Yes
Process[3]: Are you alive?
Process[5]:Yes
Process[3]: Are you alive?
Process[5]:Yes
Process[2]: Are you alive?
process[2]: -> Co-Ordinator is down
Initiating Election
Process[2] -> Process[3]  responded to election message successfully
Process[2] -> Process[4]  responded to election message successfully
Process[2] -> Process[5] did not respond to election message
Process[2] -> Process[6] did not respond to election message
Process[3] -> Process[4]  responded to election message successfully
Process[3] -> Process[5] did not respond to election message
Process[3] -> Process[6] did not respond to election message
Process[1] -> Process[2]  responded to election message successfully
Process[1] -> Process[3]  responded to election message successfully
Process[1] -> Process[4]  responded to election message successfully
Process[1] -> Process[5] did not respond to election message
Process[1] -> Process[6] did not respond to election message
Process[2] -> Process[3]  responded to election message successfully
Process[2] -> Process[4]  responded to election message successfully
Process[2] -> Process[5] did not respond to election message
Process[2] -> Process[6] did not respond to election message
Process[4] -> Process[5] did not respond to election message
Process[4] -> Process[6] did not respond to election message
New Co-Ordinator: Process[4]
Process[3]: Are you alive?
Process[4]:Yes
Process[3]: Are you alive?
Process[4]:Yes
Process[1]: Are you alive?
Process[4]:Yes
Process[2]: Are you alive?
Process[4]:Yes
Process[1]: Are you alive?
Process[4]:Yes
Process[2]: Are you alive?
Process[4]:Yes
Process[2]: Are you alive?
Process[4]:Yes
Process[2]: Are you alive?
Process[4]:Yes
Process[3]: Are you alive?
Process[4]:Yes
Process[1]: Are you alive?
Process[4]:Yes
Process[3]: Are you alive?
process[3]: -> Co-Ordinator is down
Initiating Election
Process[3] -> Process[4] did not respond to election message
Process[3] -> Process[5] did not respond to election message
Process[3] -> Process[6] did not respond to election message
New Co-Ordinator: Process[3]
New Co-Ordinator: Process[2]
Address already in use: JVM_Bind
Address already in use: JVM_Bind
Address already in use: JVM_Bind
Address already in use: JVM_Bind
Address already in use: JVM_Bind

Finally I start getting exception of Address already in use: JVM_Bin.
Also if we check with the latest elected co-ordinator in ouput just before thowing exception it elects twice before asking is co-ordinator alive?
I am sure that when a co-ordinator dies I have provided enough delay to it so that it wont wake-up in between.
When I give extra dealy then program goes ahead else it stops in the middle.
Then why this problem must be occuring?

I found the reason for the exception
It is happening because if u look closely in output just before the exception message it has elected the co-ordinator 2ce.
Whenever a Thread is elected as co-ordinator it opens a ServerSocket at port 12345.
Since it happened 2ce it might be throwing exception.
But I dont get it… why did it elect the 2ce??

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1 Answer

Editorial Team · Answer 1 · 2026-06-02T08:44:24+00:00

After refering to all the above comments I am posting the corrected code which perfectly so others can refer it.
Any improvements suggestion in the code are welcome…

package newbully;

public class NewBully {

    public static void main(String[] args) {
        int total_processes = 6;
        RunningThread[] t = new RunningThread[total_processes];
        for (int i = 0; i < total_processes; i++) {
            t[i] = new RunningThread(new Process(i+1, i+1), total_processes);//passing process id, priority, total no. of processes to running thread
        }
        try {
            Election.initialElection(t);
        } catch (NullPointerException e) {
            System.out.println(e.getMessage());
        }
        for (int i = 0; i < total_processes; i++) {
            new Thread(t[i]).start();//start every thread
        }
    }
}

package newbully;

import java.util.concurrent.locks.ReentrantLock;

public class Election {

    public static ReentrantLock pingLock = new ReentrantLock();
    public static ReentrantLock electionLock = new ReentrantLock();
    private static boolean electionFlag = false; //By default no election is going on
    private static boolean pingFlag = true; //By default I am allowed to ping 
    public static Process electionDetector;

    public static Process getElectionDetector() {
        return electionDetector;
    }

    public static void setElectionDetector(Process electionDetector) {
        Election.electionDetector = electionDetector;
    }

    public static boolean isPingFlag() {
        return pingFlag;
    }

    public static void setPingFlag(boolean pingFlag) {
        Election.pingFlag = pingFlag;
    }

    public static boolean isElectionFlag() {
        return electionFlag;
    }

    public static void setElectionFlag(boolean electionFlag) {
        Election.electionFlag = electionFlag;
    }

    public static void initialElection(RunningThread[] t) {
        Process temp = new Process(-1, -1);
        for (int i = 0; i < t.length; i++) {
            if (temp.getPriority() < t[i].getProcess().getPriority()) {
                temp = t[i].getProcess();
            }
        }
        t[temp.pid - 1].getProcess().CoOrdinatorFlag = true;
    }
}

package newbully;

import java.util.*;
import java.io.*;
import java.net.*;

public class RunningThread implements Runnable {

    private Process process;
    private int total_processes;
    private static boolean messageFlag[];
    ServerSocket[] sock;
    Random r;

    public Process getProcess() {
        return process;
    }

    public void setProcess(Process process) {
        this.process = process;
    }

    public RunningThread(Process process, int total_processes) {
        this.process = process;
        this.total_processes = total_processes;
        this.r = new Random();
        this.sock = new ServerSocket[total_processes];
        RunningThread.messageFlag = new boolean[total_processes];
        for (int i = 0; i < total_processes; i++) {
            RunningThread.messageFlag[i] = false;
        }
    }

    synchronized private void recovery() {
        while (Election.isElectionFlag());//if election is going on then wait
        System.out.println("Process[" + this.process.getPid() + "]: -> Recovered from Crash");
        //Find current co-ordinator.         
        try {
            Election.pingLock.lock();
            Election.setPingFlag(false);
            Socket outgoing = new Socket(InetAddress.getLocalHost(), 12345);
            Scanner scan = new Scanner(outgoing.getInputStream());
            PrintWriter out = new PrintWriter(outgoing.getOutputStream(), true);
            System.out.println("Process[" + this.process.getPid() + "]:-> Who is the co-ordinator?");
            out.println("Who is the co-ordinator?");
            out.flush();
            String pid = scan.nextLine();
            String priority = scan.nextLine();
            if (this.process.getPriority() > Integer.parseInt(priority)) { //Bully Condition
                out.println("Resign");
                out.flush();
                System.out.println("Process[" + this.process.getPid() + "]: Resign -> Process[" + pid + "]");
                String resignStatus = scan.nextLine();
                if (resignStatus.equals("Successfully Resigned")) {
                    this.process.setCoOrdinatorFlag(true);
                    sock[this.process.getPid() - 1] = new ServerSocket(10000 + this.process.getPid());
                    System.out.println("Process[" + this.process.getPid() + "]: -> Bullyed current co-ordinator Process[" + pid + "]");
                }
            } else {
                out.println("Don't Resign");
                out.flush();
            }
            Election.pingLock.unlock();
            return;

        } catch (IOException ex) {
            System.out.println(ex.getMessage());
        }

    }

    synchronized private void pingCoOrdinator() {
        try {
            Election.pingLock.lock();
            if (Election.isPingFlag()) {
                System.out.println("Process[" + this.process.getPid() + "]: Are you alive?");
                Socket outgoing = new Socket(InetAddress.getLocalHost(), 12345);
                outgoing.close();
            }
        } catch (Exception ex) {
            Election.setPingFlag(false);
            Election.setElectionFlag(true);
            Election.setElectionDetector(this.process);
            //Initiate Election
            System.out.println("process[" + this.process.getPid() + "]: -> Co-Ordinator is down\n" + "process[" + this.process.getPid() + "]: ->Initiating Election");
        } finally {
            Election.pingLock.unlock();
        }
    }

    private void executeJob() {
        int temp = r.nextInt(20);
        for (int i = 0; i <= temp; i++) {
            try {
                Thread.sleep((temp + 1) * 100);
            } catch (InterruptedException e) {
                System.out.println("Error Executing Thread:" + process.getPid());
                System.out.println(e.getMessage());
            }
        }
    }

    synchronized private boolean sendMessage() {
        boolean response = false;
        try {
            Election.electionLock.lock();
            if (Election.isElectionFlag() && !RunningThread.isMessageFlag(this.process.getPid() - 1) && this.process.priority >= Election.getElectionDetector().getPriority()) {

                for (int i = this.process.getPid() + 1; i <= this.total_processes; i++) {
                    try {
                        Socket electionMessage = new Socket(InetAddress.getLocalHost(), 10000 + i);
                        System.out.println("Process[" + this.process.getPid() + "] -> Process[" + i + "]  responded to election message successfully");
                        electionMessage.close();
                        response = true;
                    } catch (IOException ex) {
                        System.out.println("Process[" + this.process.getPid() + "] -> Process[" + i + "] did not respond to election message");
                    } catch (Exception ex) {
                        System.out.println(ex.getMessage());
                    }
                }
                this.setMessageFlag(true, this.process.getPid() - 1);//My message sending is done
                Election.electionLock.unlock();
                return response;
            } else {
                throw new Exception();
            }
        } catch (Exception ex1) {
            Election.electionLock.unlock();
            return true;
        }
    }

    public static boolean isMessageFlag(int index) {
        return RunningThread.messageFlag[index];
    }

    public static void setMessageFlag(boolean messageFlag, int index) {
        RunningThread.messageFlag[index] = messageFlag;
    }

    synchronized private void serve() {
        try {
            boolean done = false;
            Socket incoming = null;
            ServerSocket s = new ServerSocket(12345);
            Election.setPingFlag(true);
            int temp = this.r.nextInt(5) + 5;// min 5 requests and max 10 requests
            for (int counter = 0; counter < temp; counter++) {
                incoming = s.accept();
                if (Election.isPingFlag()) {
                    System.out.println("Process[" + this.process.getPid() + "]:Yes");
                }
                Scanner scan = new Scanner(incoming.getInputStream());
                PrintWriter out = new PrintWriter(incoming.getOutputStream(), true);
                while (scan.hasNextLine() && !done) {
                    String line = scan.nextLine();
                    if (line.equals("Who is the co-ordinator?")) {
                        System.out.println("Process[" + this.process.getPid() + "]:-> " + this.process.getPid());
                        out.println(this.process.getPid());
                        out.flush();
                        out.println(this.process.getPriority());
                        out.flush();
                    } else if (line.equals("Resign")) {
                        this.process.setCoOrdinatorFlag(false);
                        out.println("Successfully Resigned");
                        out.flush();
                        incoming.close();
                        s.close();
                        System.out.println("Process[" + this.process.getPid() + "]:-> Successfully Resigned");
                        return;
                    } else if (line.equals("Don't Resign")) {
                        done = true;
                    }
                }
            }
            //after serving 5-10 requests go down for random time
            this.process.setCoOrdinatorFlag(false);
            this.process.setDownflag(true);
            try {
                incoming.close();
                s.close();
                sock[this.process.getPid() - 1].close();
                Thread.sleep(15000);//(this.r.nextInt(10) + 1) * 10000);//going down
                recovery();
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }


        } catch (IOException ex) {
            System.out.println(ex.getMessage());
        }
    }

    @Override
    public void run() {
        try {
            sock[this.process.getPid() - 1] = new ServerSocket(10000 + this.process.getPid());
        } catch (IOException ex) {
            System.out.println(ex.getMessage());
        }
        while (true) {
            if (process.isCoOrdinatorFlag()) {
                //serve other processes
                serve();
            } else {
                while (true) {
                    //Execute some task
                    executeJob();
                    //Ping the co-ordinator
                    pingCoOrdinator();
                    //Do Election
                    if (Election.isElectionFlag()) {
                        if (!sendMessage()) {//elect self as co-ordinator
                            Election.setElectionFlag(false);//Election is Done
                            System.out.println("New Co-Ordinator: Process[" + this.process.getPid() + "]");
                            this.process.setCoOrdinatorFlag(true);
                            for (int i = 0; i < total_processes; i++) {
                                RunningThread.setMessageFlag(false, i);
                            }
                            break;
                        }
                    }
                }
            }
        }
    }
}

package newbully;

public class Process {

    int pid;
    boolean downflag,CoOrdinatorFlag;

    public boolean isCoOrdinatorFlag() {
        return CoOrdinatorFlag;
    }

    public void setCoOrdinatorFlag(boolean isCoOrdinator) {
        this.CoOrdinatorFlag = isCoOrdinator;
    }
    int priority;

    public boolean isDownflag() {
        return downflag;
    }

    public void setDownflag(boolean downflag) {
        this.downflag = downflag;
    }

    public int getPid() {
        return pid;
    }

    public void setPid(int pid) {
        this.pid = pid;
    }

    public int getPriority() {
        return priority;
    }

    public void setPriority(int priority) {
        this.priority = priority;
    }

    public Process() {
    }

    public Process(int pid, int priority) {
        this.pid = pid;
        this.downflag = false;
        this.priority = priority;
        this.CoOrdinatorFlag = false;
    }
}

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I am writing a program for Bully Algorithm in Java Here is the code:

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