An essential Julian Day Program

import java.io.*;
public class JulianNumber
{
    int d,m,y;
    int n;
    void input()throws IOException
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        System.out.println("enter the date in dd mm yyyy format");
        d=Integer.parseInt(br.readLine());
        m=Integer.parseInt(br.readLine());
        y=Integer.parseInt(br.readLine());
        if(m<=12&&d<=31)
        {
            compute();
        }
        else
            System.out.println("Invalid date");
    }

    void compute()
    {
        int arr[]={31,28,31,30,31,30,31,31,30,31,30,31};
        if(y%4==0)
            arr[1]=29;
        for(int i=0;i<m-1;i++)
        { 
            n+=arr[i];
        }
        n=n+d;
        System.out.println("The Julian day is:   "+n);
    }

    public static void main()throws IOException
    {
        JulianNumber obj=new JulianNumber();
        obj.input();
    }
}