// : c11:Statistics.java
// Simple demonstration of HashMap.
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
class Counter {
int i = 1;
public String toString() {
return Integer.toString(i);
}
}
public class Statistics {
private static Random rand = new Random();
public static void main(String[] args) {
Map hm = new HashMap();
for (int i = 0; i < 10000; i++) {
// Produce a number between 0 and 20:
Integer r = new Integer(rand.nextInt(20));
if (hm.containsKey(r))
((Counter) hm.get(r)).i++;
else
hm.put(r, new Counter());
}
System.out.println(hm);
}
} ///:~