import java.util.Date;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.text.ParseException;
import java.util.Calendar;
import java.util.concurrent.TimeUnit;

class Ideone
{
  
  public static void main(String[] args)
  {
    try {
    	System.out.print( diferencaHoras("02/01/2018 23:00", "03/01/2018 12:00") );
    } catch(Exception e) {
      	System.out.println(e.getMessage());
    }
  }
  
  public static int diferencaHoras(String h1, String h2) throws ParseException{

	/* Alteração */
    DateFormat df = new SimpleDateFormat("dd/MM/yyyy HH:mm");

    Date d1 = df.parse (h1);
    Date d2 = df.parse (h2);

    long diff = d1.getTime() - d2.getTime();
    
    int diffHours = (int) (diff / (60 * 60 * 1000));

    return diffHours;
  }
}