Java Map Interface

Java Map Interface is an object that maps keys to values. A map cannot contain duplicate keys: Each key can map to at most one value. It models the mathematical function abstraction. The following program generates a frequency table of the words found in its argument list. The frequency table maps each word to the number of times it occurs in the argument list. import java.util.*; public class Freq { public static void main(String[] args) { Map m = new HashMap(); // Initialize frequency table from command line for (String a : args) { Integer freq = m.get(a); m.put(a, (freq == null) ? 1 : freq + 1); } System.out.println(m.size() + " distinct words:");