// equalshashcode/SpringDetector.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.
// What will the weather be?
import java.util.*;
import java.util.stream.*;
import java.util.function.*;
import java.lang.reflect.*;

public class SpringDetector {
 public static <T extends Groundhog>
 void detectSpring(Class<T> type) {
 try {
 Constructor<T> ghog =
 type.getConstructor(int.class);
 Map<Groundhog, Prediction> map =
 IntStream.range(0, 10)
 .mapToObj(i -> {
 try {
 return ghog.newInstance(i);
 } catch(Exception e) {
 throw new RuntimeException(e);
 }
 })
 .collect(Collectors.toMap(
 Function.identity(),
 gh -> new Prediction()));
 map.forEach((k, v) ->
 System.out.println(k + ": " + v));
 Groundhog gh = ghog.newInstance(3);
 System.out.println(
 "Looking up prediction for " + gh);
 if(map.containsKey(gh))
 System.out.println(map.get(gh));
 else
 System.out.println("Key not found: " + gh);
 } catch(NoSuchMethodException |
 IllegalAccessException |
 InvocationTargetException |
 InstantiationException e) {
 throw new RuntimeException(e);
 }
 }
 public static void main(String[] args) {
 detectSpring(Groundhog.class);
 }
}
/* Output:
Groundhog #3: Six more weeks of Winter!
Groundhog #0: Early Spring!
Groundhog #8: Six more weeks of Winter!
Groundhog #6: Early Spring!
Groundhog #4: Early Spring!
Groundhog #2: Six more weeks of Winter!
Groundhog #1: Early Spring!
Groundhog #9: Early Spring!
Groundhog #5: Six more weeks of Winter!
Groundhog #7: Six more weeks of Winter!
Looking up prediction for Groundhog #3
Key not found: Groundhog #3
*/