// streams/MapCollector.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
import java.util.*;
import java.util.stream.*;

class Pair {
 public final Character c;
 public final Integer i;
 Pair(Character c, Integer i) {
 this.c = c;
 this.i = i;
 }
 public Character getC() { return c; }
 public Integer getI() { return i; }
 @Override
 public String toString() {
 return "Pair(" + c + ", " + i + ")";
 }
}

class RandomPair {
 Random rand = new Random(47);
 // An infinite iterator of random capital letters:
 Iterator<Character> capChars = rand.ints(65,91)
 .mapToObj(i -> (char)i)
 .iterator();
 public Stream<Pair> stream() {
 return rand.ints(100, 1000).distinct()
 .mapToObj(i -> new Pair(capChars.next(), i));
 }
}

public class MapCollector {
 public static void main(String[] args) {
 Map<Integer, Character> map =
 new RandomPair().stream()
 .limit(8)
 .collect(
 Collectors.toMap(Pair::getI, Pair::getC));
 System.out.println(map);
 }
}
/* Output:
{688=W, 309=C, 293=B, 761=N, 858=N, 668=G, 622=F,
751=N}
*/