// 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

*/