Is there a faster method to match an arbitrary String to month name in Java

Question

I want to determine if a string is the name of a month and I want to do it relatively quickly. The function that is currently stuck in my brain is something like:

boolean isaMonth( String str ) {
    String[] months = DateFormatSymbols.getInstance().getMonths();
    String[] shortMonths = DateFormatSymbols.getInstance().getShortMonths();
    int i;

    for( i = 0; i<months.length(); ++i;) {
        if( months[i].equals(str) ) return true;
        if( shortMonths[i].equals(str ) return true;
    }
    return false;
}

However, I will be processing lots of text, passed one string at a time to this function, and most of the time I will be getting the worst case of going through the entire loop and returning false.

I saw another question that talked about a Regex to match a month name and a year which could be adapted for this situation. Would the Regex be faster? Is there any other solution that might be faster?

Answer 1

Why not store the month names in a HashSet? This will give you constant time lookup instead of the linear time lookup you are getting from your loop.

import java.util.HashSet;
import java.util.Collections;
import java.text.DateFormatSymbols;

class Test {
  public static void main(String[] args) {

    HashSet<String> months = new HashSet<String>(24);  

    Collections.addAll(months, DateFormatSymbols.getInstance().getMonths());
    Collections.addAll(months, DateFormatSymbols.getInstance().getShortMonths());

    System.out.println(months.contains(args[0]));

  }
}