How is the user inputting the month? As an int (11 for November)? Then you would use the set method and subtract one from the input.
Of course you would add some error checking on the user input.
If user input is a String ("November" or some variant) then you would need some way to parse the String into its int equivalent.
DateFormatSymbols dfs = new DateFormatSymbols();
String[] months = dfs.getMonths();
for(int index = 0; index < months; index++) {
if(months[index].equals(userInput)) {
return index;
}
}
return -1; // indicates invalid month entered