Banker's Algorithm Implementation in Java

/*
PROGRAM: BANKER'S ALGORITHM Implementation

*/

import java.io.*;
import java.util.*;
class Banker
{
 static int safe[]=new int[20];
 static boolean safety(int a[],int al[][],int need[][],int n1,int m1)
 {
int n=n1;
int m=m1;
int nd[][]=new int[n][m];
int work[]=new int[m];
int all[][]=new int[n][m];

for(int i=0;i<m;i++)
work[i]=a[i];

for(int i=0;i<n;i++)
for(int j=0;j<m;j++)
all[i][j]=al[i][j];

for(int i=0;i<n;i++)
for(int j=0;j<m;j++)
nd[i][j]=need[i][j];

boolean fin[]=new boolean[n];

for(int i=0;i<n;i++)
fin[i]=false;

int check=0;
int check1=0;

do
{
for(int i=0;i<n;i++)
{
boolean flag=true;
if(fin[i]==false)
{
for(int j=0;j<m;j++)
{if(work[j]<nd[i][j])
flag=false;
}
if(flag)
{
for(int j=0;j<m;j++)
work[j]+=all[i][j];
safe[check]=i;
check++;
fin[i]=true;
}
}

}

check1++;
}while(check<n && check1<n);


if(check>n)
return false;
else
return true;



 }

static boolean reqFunc(int a[],int al[][],int need[][],int req[],int pid,int n1,int m1)
{
 int n=n1;
 int m=m1;
 int avail[]=new int[m];
int alloc[][]=new int[n][m];
int need1[][]=new int[n][m];
int req1[]=new int[m];
int r=pid;

       for(int i=0;i<m;i++)
req1[i]=req[i];

for(int i=0;i<m;i++)
avail[i]=a[i];

        for(int i=0;i<n;i++)
for(int j=0;j<m;j++)
alloc[i][j]=al[i][j];

for(int i=0;i<n;i++)
for(int j=0;j<m;j++)
need1[i][j]=need[i][j];

boolean flag=true;
for(int i=0;i<m;i++)
{
if(need1[r][i]<req1[i])
flag=false;
}

if(flag)
{
for(int i=0;i<m;i++)
if(avail[i]<req1[i])
flag=false;

if(flag)
{
for(int i=0;i<m;i++)
{
alloc[r][i]+=req1[i];
need1[r][i]-=req1[i];
avail[i]-=req1[i];
}

if(safety(avail,alloc,need1,n,m))
return true;
else
System.out.println("It leads to deadlock ,so request can't be granted");
}
else
System.out.println("process p"+r+"should wait");
}
else
System.out.println("Error:process exceeding Limit");
return false;


}

public static void main(String args[])throws IOException
{
InputStreamReader isr=new InputStreamReader(System.in);
BufferedReader obj=new BufferedReader(isr);

int n,m;
System.out.println("enter no. of processes:");
n=Integer.parseInt(obj.readLine());
System.out.println("enter no. of resources:");
m=Integer.parseInt(obj.readLine());

int a[]=new int[m];
for(int i=0;i<m;i++)
{
System.out.println("enter no. of available instances resources:"+i);
a[i]=Integer.parseInt(obj.readLine());

}

System.out.println("enter allocation of resources:");
int al[][]=new int[n][m];
for(int i=0;i<n;i++)
for(int j=0;j<m;j++)
{
System.out.println("enter allocation instances of resources:"+j+"for process p"+i);
al[i][j]=Integer.parseInt(obj.readLine());

}

System.out.println("enter maximum of resources:");
int max[][]=new int[n][m];
for(int i=0;i<n;i++)
for(int j=0;j<m;j++)
{
System.out.println("enter max instances of resources:"+j+"for process p"+i);
max[i][j]=Integer.parseInt(obj.readLine());

}


int need[][]=new int[n][m];
for(int i=0;i<n;i++)
for(int j=0;j<m;j++)
{

need[i][j]=max[i][j]-al[i][j];

}

if(safety(a,al,need,n,m))
{
System.out.println("System in Safe State");
System.out.println("System's Safe sequence:");
for(int i=0;i<n;i++)
System.out.println(safe[i]+" ");
}

else
System.out.println("System in UnSafe State");

System.out.println("do u wanna to hav a request for any process,then enter Process no. and Requesting resources");
int pid=Integer.parseInt(obj.readLine());
int req[]=new int[m];
for(int i=0;i<m;i++)
req[i]=Integer.parseInt(obj.readLine());
if(reqFunc(a,al,need,req,pid,n,m))
{
System.out.println("request can be granted");
for(int i=0;i<m;i++)
{al[pid][i]+=req[i];
need[pid][i]-=req[i];
a[i]-=req[i];

}
        if(safety(a,al,need,n,m))
{
System.out.println("System in Safe State");
System.out.println("System's Safe sequence:");
for(int i=0;i<n;i++)
System.out.println(safe[i]+" ");
}
else
System.out.println("System in UnSafe State");
}

}
}

/*
OUTPUT:

C:\Program Files\Java\jdk1.6.0_02\bin>java Banker
enter no. of processes:
5
enter no. of resources:
3
enter no. of available instances resources:0
3
enter no. of available instances resources:1
3
enter no. of available instances resources:2
2
enter allocation of resources:
enter allocation instances of resources:0for process p0
0
enter allocation instances of resources:1for process p0
1
enter allocation instances of resources:2for process p0
0
enter allocation instances of resources:0for process p1
2
enter allocation instances of resources:1for process p1
0
enter allocation instances of resources:2for process p1
0
enter allocation instances of resources:0for process p2
3
enter allocation instances of resources:1for process p2
0
enter allocation instances of resources:2for process p2
2
enter allocation instances of resources:0for process p3
2
enter allocation instances of resources:1for process p3
1
enter allocation instances of resources:2for process p3
1
enter allocation instances of resources:0for process p4
0
enter allocation instances of resources:1for process p4
0
enter allocation instances of resources:2for process p4
2
enter maximum of resources:
enter max instances of resources:0for process p0
7
enter max instances of resources:1for process p0
5
enter max instances of resources:2for process p0
3
enter max instances of resources:0for process p1
3
enter max instances of resources:1for process p1
2
enter max instances of resources:2for process p1
2
enter max instances of resources:0for process p2
9
enter max instances of resources:1for process p2
0
enter max instances of resources:2for process p2
2
enter max instances of resources:0for process p3
2
enter max instances of resources:1for process p3
2
enter max instances of resources:2for process p3
2
enter max instances of resources:0for process p4
4
enter max instances of resources:1for process p4
3
enter max instances of resources:2for process p4
3
System in Safe State
System's Safe sequence:
1
3
4
0
2
do u wanna to hav a request for any process,then enter Process no. and Requestin
g resources
4
3
3
0
request can be granted
System in Safe State
System's Safe sequence:
1
3
4
0
2
*/

Source:http://demlaip.wordpress.com/2009/09/20/bankers-algorithm-implementation-in-java/