I try to find number of days using following method,

public static int findNoOfDays(int year, int month, int day) {
        Calendar calendar = Calendar.getInstance();
        calendar.set(year, month - 1, day);
        int days = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
        return days;
    }

likewise I want to get the number of days by giving start date and end date and get the number of days excluding Saturday and Sunday.

Here is a method that calculates the number of days between two dates:

private int calculateNumberOfDaysBetween(Date startDate, Date endDate) {
    if (startDate.after(endDate)) {
        throw new IllegalArgumentException("End date should be grater or equals to start date");
    }

    long startDateTime = startDate.getTime();
    long endDateTime = endDate.getTime();
    long milPerDay = 1000*60*60*24; 

    int numOfDays = (int) ((endDateTime - startDateTime) / milPerDay); // calculate vacation duration in days

    return ( numOfDays + 1); // add one day to include start date in interval
}

And here is a method that calculates the number of weekent days in the specified time period:

private static int calculateNumberOfWeekendsInRange(Date startDate, Date endDate) {
    Calendar calendar = Calendar.getInstance();
    calendar.setTime(startDate);

    int counter = 0;
    while(!calendar.getTime().after(endDate)) {
        int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK);
        if (dayOfWeek==1 || dayOfWeek==7) {
            counter++;
        }
        calendar.add(Calendar.DAY_OF_MONTH, 1);
    }

    return counter;
}

EDIT:

I changed last method, now it calculates the number of days exclude weekend days:

private int calculateNumberOfDaysExcludeWeekends(Date startDate, Date endDate) {
    if (startDate.after(endDate)) {
        throw new IllegalArgumentException("End date should be grater or equals to start date");
    }

    Calendar calendar = Calendar.getInstance();
    calendar.setTime(startDate);

    int numOfDays = 0;
    while(!calendar.getTime().after(endDate)) {
        int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK);
        if ( (dayOfWeek>1) && (dayOfWeek<7) ) {
            numOfDays++;
        }
        calendar.add(Calendar.DAY_OF_MONTH, 1);
    }

    return numOfDays;
}