I solved it. Thanks to help.
The Edited Program is,
class Area
{
public static void main(String args[])
{
int s,sum=0,n,ss,m=1;
double area;
n=args.length;
int []a=new int [n];
for(int i=0;i<n;i++)
{
if(n==3)
{
a[i]=Integer.parseInt(args[i]);
}
else
{
System.out.println("Please Enter Only Three Values");
break;
}
sum=sum+a[i];
}
if(n==3)
{
s=sum/2;
for(int i=0;i<n;i++)
{
ss=(s-a[i]);
m=m*ss;
}
area=Math.sqrt(s*m);
System.out.println("Area of Triangle = "+area);
}
}
}