63 lines
1.8 KiB
Java
63 lines
1.8 KiB
Java
// equalshashcode/SpringDetector.java
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// (c)2020 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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// What will the weather be?
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import java.util.*;
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import java.util.stream.*;
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import java.util.function.*;
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import java.lang.reflect.*;
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public class SpringDetector {
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public static <T extends Groundhog>
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void detectSpring(Class<T> type) {
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try {
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Constructor<T> ghog =
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type.getConstructor(int.class);
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Map<Groundhog, Prediction> map =
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IntStream.range(0, 10)
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.mapToObj(i -> {
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try {
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return ghog.newInstance(i);
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} catch(Exception e) {
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throw new RuntimeException(e);
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}
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})
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.collect(Collectors.toMap(
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Function.identity(),
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gh -> new Prediction()));
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map.forEach((k, v) ->
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System.out.println(k + ": " + v));
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Groundhog gh = ghog.newInstance(3);
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System.out.println(
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"Looking up prediction for " + gh);
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if(map.containsKey(gh))
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System.out.println(map.get(gh));
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else
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System.out.println("Key not found: " + gh);
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} catch(NoSuchMethodException |
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IllegalAccessException |
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InvocationTargetException |
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InstantiationException e) {
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throw new RuntimeException(e);
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}
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}
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public static void main(String[] args) {
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detectSpring(Groundhog.class);
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}
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}
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/* Output:
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Groundhog #3: Six more weeks of Winter!
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Groundhog #0: Early Spring!
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Groundhog #8: Six more weeks of Winter!
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Groundhog #6: Early Spring!
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Groundhog #4: Early Spring!
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Groundhog #2: Six more weeks of Winter!
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Groundhog #1: Early Spring!
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Groundhog #9: Early Spring!
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Groundhog #5: Six more weeks of Winter!
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Groundhog #7: Six more weeks of Winter!
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Looking up prediction for Groundhog #3
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Key not found: Groundhog #3
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*/
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