OnJava8-Examples/collections/Statistics.java at master · CSapprenticeWT/OnJava8-Examples · GitHub

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// collections/Statistics.java

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

// Simple demonstration of HashMap

import java.util.*;

public class Statistics {

public static void main(String[] args) {

Random rand = new Random(47);

Map<Integer, Integer> m = new HashMap<>();

for(int i = 0; i < 10000; i++) {

// Produce a number between 0 and 20:

int r = rand.nextInt(20);

Integer freq = m.get(r); // [1]

m.put(r, freq == null ? 1 : freq + 1);

}

System.out.println(m);

}

/* Output:

{0=481, 1=502, 2=489, 3=508, 4=481, 5=503, 6=519,

7=471, 8=468, 9=549, 10=513, 11=531, 12=521, 13=506,

14=477, 15=497, 16=533, 17=509, 18=478, 19=464}