Implementation of Banker’s Algorithm in JAVA

The program will read a data file. The name of the data file will be provided as a command line argument. The data file will have the following structure:
First row will represent the maximum units of each resource. There can be any number of resources.
Second row will contain new request by a process. The first number will be PID i.e process ID of the process making the request and subsequent numbers will be the amount/number of units of each resource the process is requesting.
Subsequent rows will contain Allocation & Max information about each process. An example file is as follows:

10 5 7

1 1 0 2
0 1 0 7 5 3
2 0 0 3 2 2
3 0 2 9 0 2
2 1 1 2 2 2
0 0 2 4 3 3
In the above file, the first line tells us that there are 10 units of resource R1, 5 units of R2 and 7 units of R3 in the system.
The second line tells that process P1 has requested 1 unit of resource R1, 0 units of R2 and 2 units of R3.
The third line tells that process P0 has been allocated 0 units of R1, 1 unit of R2 and 0 units of R3; and maximum demand of P0 is 7 units of R1, 5 units of R2 and 3 units of R3.

Code:

import java.util.*;

import java.io.*;


public class Banker{


  public static void main(String args[])  throws IOException{


   int total[]=null,line=1,newRequest[]=null,pid=0,resources=0,available[]=null;

   ArrayList<int[]> allocation = new ArrayList<int[]>();

   ArrayList<int[]> demand = new ArrayList<int[]>();

   ArrayList<int[]> need = new ArrayList<int[]>();

   ArrayList<String> sequence = new ArrayList<String>();

   boolean[] completedProcess=null;


  if(args.length==0){

  System.out.println("File Not Provided");

  return;

 }


  Scanner scanner = new Scanner(new File(args[0]));


  while(scanner.hasNextLine()){

  String str = scanner.nextLine();

  String arr[];


   if(line>2){

   arr = str.trim().split("\\s+");


    int allocated[]=new int[resources];

   int processDemand[]=new int[resources];


    for(int i=0;i<arr.length;i++){


     if(i<(arr.length/2)){

     allocated[i]=Integer.parseInt(arr[i]);

     available[i]=available[i]-allocated[i];

    }else

     processDemand[i-(arr.length/2)]=Integer.parseInt(arr[i]);

   }

   allocation.add(allocated);

   demand.add(processDemand);

   continue;

  }


   if(line==1){

   arr = str.trim().split("\\s+");

   total = new int[arr.length];

   available = new int[arr.length];

   resources = arr.length;


    for(int i=0;i<arr.length;i++){

    total[i] = Integer.parseInt(arr[i]);

   }

   available = Arrays.copyOf(total,total.length);

   line++;

  }else if(line==2){

   arr = str.trim().split("\\s+");

   newRequest = new int[arr.length];

   for(int i=0;i<arr.length;i++){

    newRequest[i] = Integer.parseInt(arr[i]);

   }

   line++;

  }

 }


  for(int i=0;i<allocation.size();i++){

  int allocated[] = allocation.get(i);

  int processDemand[] = demand.get(i);

  int needOfProcess[] = new int[allocated.length];


   for(int j=0;j<allocated.length;j++){

   needOfProcess[j]=processDemand[j]-allocated[j];

  }


   need.add(needOfProcess);

 } 


  boolean flag = false;

 completedProcess = new boolean[allocation.size()];


  for(int i=1;i<newRequest.length;i++){

  if(newRequest[i]<=available[i-1]){

   flag = true;

  }else{

   flag = false;

   break;

  }

 }


  if(flag){

  int[] allocated,needOfProcess;

  allocated = allocation.get(newRequest[0]);

  needOfProcess = need.get(newRequest[0]);

  for(int i=0;i<available.length;i++){

   allocated[i]+=newRequest[i+1];

   available[i]-=newRequest[i+1];

   needOfProcess[i]-=newRequest[i+1];

  }

 }else{

  System.out.println("\nNot enough resources: Request Denied");

  return;

 }


  int totalCompletedProcess=0;

 int completedProcessLastTime=-1;


  while(!isAllTrue(completedProcess)){

  flag=false;


   if(totalCompletedProcess==completedProcessLastTime){

   System.out.println("\nNo sequence to satisfy safety criteria: Request Denied");

   return;

  }


   completedProcessLastTime=totalCompletedProcess;


   for(int i=0;i<need.size();i++){


    if(completedProcess[i])

    continue;


    int[] needOfProcess = need.get(i);


    for(int j=0;j<available.length;j++){

    if(needOfProcess[j]<=available[j]){

     flag = true;

    }else{

     flag = false;

     break;

    }

   }


    if(flag){

    int[] allocated;

    allocated = allocation.get(i);


     for(int j=0;j<available.length;j++){

     available[j]+=allocated[j];

     allocated[j]-=allocated[j];

     needOfProcess[j]-=needOfProcess[j];

    }


     completedProcess[i]=true;

    totalCompletedProcess++;

    sequence.add("P"+i+" ");

   }


   }

 }


  System.out.println("\nSequence "+sequence.toString()+" satisfy safety criteria: Request Granted");

 

  }


  public static boolean isAllTrue(boolean[] completedProcess){

   for(int i=0;i<completedProcess.length;i++){

    if(!completedProcess[i]){

     return false;

    }

   }

   return true;

  }

}

Output:

The output of each run will either produce a sequence of processes that satisfies the safety criteria if we grant the request or report that this request should not be granted and the reason for denial.

Java Banker Input.txt

Sequence [P1 , P3 , P4 , P0 , P2 ] satisfy safety criteria: Request Granted

If the second line in the above file is modified to

4 3 3 0

Java Banker Input.txt

No sequence to satisfy safety criteria: Request Denied

If the second line in the above file is modified to

1 1 0 5

Java Banker Input.txt

Not enough resources: Request Denied

Implementation of Banker’s Algorithm in JAVA

Code:

Output:

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