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:


  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
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

No comments