Write a program to closest prime number to any input number ?

package test;
import java.util.*;

public class closestprime {
public static boolean isprime(int a)
{int c=0;
for(int i=2;i<a/2;i++)
{
if(a%i==0)
{
c=1;
}
}

if(c==1)
         return false;
else
return true;


}

public static void main(String[] arg)
{
Scanner sc=new Scanner(System.in);
int a=sc.nextInt();
int i;
int n,n1,d,d1;
for(i=a+1;;i++)
{
if(isprime(i))
{    n=i;
    d=i-a;

break;
}
}
for(i=a-1;;i--)
{
if(isprime(i))
{    d1=a-i;
n1=i;

break;
}
}
if(d>d1)
System.out.println("closest prime no.: "+n1);
else if(d1>d)
System.out.println("closest prime no.: "+n);
else
System.out.println("closest prime no.: "+n+" "+n1);
}

}