java program to implement Banker's algorithm

import java.io.*;

 public class Bankers 

{ 

static int safe_sequence[]; 

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

{ 

BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); 

System.out.println("Please enter the total number of Resources: "); 

int res_n = Integer.parseInt(br.readLine()); 

int res[] = new int[res_n]; 

int cur_avail[] = new int[res_n]; 

for(int i = 0; i < res_n; i++) 

{ 

System.out.println("Enter total number of instances for Resource" + (i+1) + ":");
            res[i] = Integer.parseInt(br.readLine());
            cur_avail[i] = res[i];
        }

        System.out.println("Enter number of processes:");
        int pros_n = Integer.parseInt(br.readLine());
   
        safe_sequence = new int[pros_n];
        int max[][] = new int[res_n][pros_n];
        int alloc[][] = new int[res_n][pros_n];
   
        for(int i = 0; i < pros_n; i++)
        {
         System.out.println("Enter the Maximum string for Process " + (i+1) + ":");
         String ip = br.readLine();
         for(int j = 0; j < res_n; j++)
         {
          max[j][i] = Integer.parseInt(String.valueOf(ip.charAt(j)));
         }
        }
   
        for(int i=0;i<pros_n;i++)
        {
         System.out.println("Enter the Allocation string for Process " + (i+1)

         + ":");
         String ip = br.readLine();
         for(int j = 0; j < res_n; j++)
         {
          alloc[j][i] = Integer.parseInt(String.valueOf(ip.charAt(j)));
          cur_avail[j] = cur_avail[j] - alloc[j][i];
         }
        }
   
   
       
        int need[][] = new int[res_n][pros_n];
 
     
        for(int i = 0; i < pros_n; i++)  //need loop
        {
         for(int j = 0; j < res_n; j++)
         {
          need[j][i] = max[j][i] - alloc[j][i];
         }
        }
       
        boolean safe = check_state(need, alloc, cur_avail, res_n, pros_n);
        System.out.println();
       
        if(safe)
        {
         System.out.println("The system is in a Safe State.");
         System.out.print("The Safe Sequence is: ");
         for(int i = 0; i < pros_n; i++)
          System.out.print("P" + (safe_sequence[i] + 1) + " ");
         System.out.println();
        }
        else
         System.out.println("The system is not in a Safe State.");
       
        if(safe)
        {
         System.out.println();
        

         System.out.println("Please enter the number of the Process that is

         requesting more resources: ");
        

         int req_n = Integer.parseInt(br.readLine()) - 1;
         int req[] = new int[res_n];
         System.out.println("Please enter the Request Matrix: ");
         String ip = br.readLine();
         int need_count = 0, avl_count = 0;
         for(int i = 0; i < res_n; i++)
         {
          req[i] = Integer.parseInt(String.valueOf(ip.charAt(i)));
          if(req[i] <= need[i][req_n])
           need_count++;
          if(req[i] <= cur_avail[i])
           avl_count++;
         }
         if(need_count != res_n)
       

          System.out.println("The request cannot be granted since requested

          resources are more than previously declared Maximum.");
       

          if(avl_count != res_n)
       

         System.out.println("The request cannot be granted since the amount

         of resources requested are not available.");
         

        if(need_count == res_n && avl_count == res_n)
         {
          for(int i = 0; i < res_n; i++)
          {
           alloc[i][req_n] += req[i];
           need[i][req_n] -= req[i];
           cur_avail[i] -= req[i];
          }
          safe = check_state(need, alloc, cur_avail, res_n, pros_n);
          System.out.println();
         
          if(safe)
                {
                 System.out.println("The system will be in a Safe State if

                 the request is granted.");
                

                 System.out.print("The Safe Sequence is: ");
                 for(int i = 0; i < pros_n; i++)
                  System.out.print("P" + (safe_sequence[i] + 1) + " ");
                 System.out.println();
                }
                else
                 System.out.println("The system will not be in a Safe State if

                 the request is granted.");
         
         }
        }
       
    }
   
    static boolean check_state(int need[][], int alloc[][], int cur_avail[],

    int res_n, int pros_n)
    {
     boolean marked[]= new boolean[pros_n];
        int safe_pos = 0;
        boolean safe = true;
        int avail[] = new int[res_n];
        for(int i = 0; i < res_n; i++)
         avail[i] = cur_avail[i];
        while(safe_pos < pros_n && safe)
        {
         for(int i = 0; i < pros_n; i++)
            {
             int c = 0;
             for(int j = 0; j < res_n; j++)
             {
              if(need[j][i] <= avail[j])
               c++;
             }
             if((c == res_n) && (marked[i] == false)) 
             {
              for(int j = 0; j < res_n; j++)
              {
               avail[j] += alloc[j][i];
              }
              marked[i] = true;
              safe_sequence[safe_pos] = i;
              safe_pos++;
              break;
             }
             if(i == pros_n - 1 && c < res_n)
             {
              safe = false;
             }
            }
        }
        return safe;
    }
   
}