How do I count the frequency of some word/object?
Created May 4, 2012
John Zukowski
The Map interface can be used to count the number of times a word/object appears. The following program demonstrates counting word frequency from the command line:
import java.util.*; public class MapExample { public static void main(String args[]) { Map map = new HashMap(); Integer ONE = new Integer(1); for (int i=0, n=args.length; i<n; i++) { String key = args[i]; Integer frequency = (Integer)map.get(key); if (frequency == null) { frequency = ONE; } else { int value = frequency.intValue(); frequency = new Integer(value + 1); } map.put(key, frequency); } System.out.println(map); Map sortedMap = new TreeMap(map); System.out.println(sortedMap); } }