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1 /*
2  * Copyright (C) 2012 The Guava Authors
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.google.common.testing;
18 
19 import static com.google.common.truth.Truth.assertThat;
20 import static org.junit.Assert.assertThrows;
21 
22 import com.google.common.base.CharMatcher;
23 import com.google.common.base.Charsets;
24 import com.google.common.base.Equivalence;
25 import com.google.common.base.Joiner;
26 import com.google.common.base.Predicate;
27 import com.google.common.base.Splitter;
28 import com.google.common.base.Stopwatch;
29 import com.google.common.base.Ticker;
30 import com.google.common.collect.BiMap;
31 import com.google.common.collect.ClassToInstanceMap;
32 import com.google.common.collect.ImmutableBiMap;
33 import com.google.common.collect.ImmutableClassToInstanceMap;
34 import com.google.common.collect.ImmutableCollection;
35 import com.google.common.collect.ImmutableList;
36 import com.google.common.collect.ImmutableListMultimap;
37 import com.google.common.collect.ImmutableMap;
38 import com.google.common.collect.ImmutableMultimap;
39 import com.google.common.collect.ImmutableMultiset;
40 import com.google.common.collect.ImmutableSet;
41 import com.google.common.collect.ImmutableSetMultimap;
42 import com.google.common.collect.ImmutableSortedMap;
43 import com.google.common.collect.ImmutableSortedSet;
44 import com.google.common.collect.ImmutableTable;
45 import com.google.common.collect.ListMultimap;
46 import com.google.common.collect.MapDifference;
47 import com.google.common.collect.Multimap;
48 import com.google.common.collect.Multiset;
49 import com.google.common.collect.PeekingIterator;
50 import com.google.common.collect.Range;
51 import com.google.common.collect.RowSortedTable;
52 import com.google.common.collect.SetMultimap;
53 import com.google.common.collect.SortedMapDifference;
54 import com.google.common.collect.SortedMultiset;
55 import com.google.common.collect.SortedSetMultimap;
56 import com.google.common.collect.Table;
57 import com.google.common.io.ByteSink;
58 import com.google.common.io.ByteSource;
59 import com.google.common.io.CharSink;
60 import com.google.common.io.CharSource;
61 import com.google.common.primitives.UnsignedInteger;
62 import com.google.common.primitives.UnsignedLong;
63 import com.google.common.util.concurrent.AtomicDouble;
64 import java.io.ByteArrayInputStream;
65 import java.io.ByteArrayOutputStream;
66 import java.io.File;
67 import java.io.IOException;
68 import java.io.InputStream;
69 import java.io.OutputStream;
70 import java.io.PrintStream;
71 import java.io.PrintWriter;
72 import java.io.Reader;
73 import java.io.StringReader;
74 import java.io.StringWriter;
75 import java.io.Writer;
76 import java.lang.reflect.AnnotatedElement;
77 import java.lang.reflect.GenericDeclaration;
78 import java.lang.reflect.Type;
79 import java.math.BigDecimal;
80 import java.math.BigInteger;
81 import java.nio.Buffer;
82 import java.nio.ByteBuffer;
83 import java.nio.CharBuffer;
84 import java.nio.DoubleBuffer;
85 import java.nio.FloatBuffer;
86 import java.nio.IntBuffer;
87 import java.nio.LongBuffer;
88 import java.nio.ShortBuffer;
89 import java.nio.charset.Charset;
90 import java.util.ArrayList;
91 import java.util.BitSet;
92 import java.util.Collection;
93 import java.util.Comparator;
94 import java.util.Currency;
95 import java.util.Deque;
96 import java.util.HashMap;
97 import java.util.Iterator;
98 import java.util.LinkedList;
99 import java.util.List;
100 import java.util.ListIterator;
101 import java.util.Locale;
102 import java.util.Map;
103 import java.util.NavigableMap;
104 import java.util.NavigableSet;
105 import java.util.PriorityQueue;
106 import java.util.Queue;
107 import java.util.Random;
108 import java.util.Set;
109 import java.util.SortedMap;
110 import java.util.SortedSet;
111 import java.util.TreeMap;
112 import java.util.TreeSet;
113 import java.util.UUID;
114 import java.util.concurrent.BlockingDeque;
115 import java.util.concurrent.BlockingQueue;
116 import java.util.concurrent.ConcurrentMap;
117 import java.util.concurrent.ConcurrentNavigableMap;
118 import java.util.concurrent.DelayQueue;
119 import java.util.concurrent.Executor;
120 import java.util.concurrent.PriorityBlockingQueue;
121 import java.util.concurrent.SynchronousQueue;
122 import java.util.concurrent.ThreadFactory;
123 import java.util.concurrent.TimeUnit;
124 import java.util.concurrent.atomic.AtomicBoolean;
125 import java.util.concurrent.atomic.AtomicInteger;
126 import java.util.concurrent.atomic.AtomicLong;
127 import java.util.concurrent.atomic.AtomicReference;
128 import java.util.regex.MatchResult;
129 import java.util.regex.Pattern;
130 import junit.framework.TestCase;
131 import org.checkerframework.checker.nullness.qual.Nullable;
132 
133 /**
134  * Unit test for {@link ArbitraryInstances}.
135  *
136  * @author Ben Yu
137  */
138 public class ArbitraryInstancesTest extends TestCase {
139 
testGet_primitives()140   public void testGet_primitives() {
141     assertNull(ArbitraryInstances.get(void.class));
142     assertNull(ArbitraryInstances.get(Void.class));
143     assertEquals(Boolean.FALSE, ArbitraryInstances.get(boolean.class));
144     assertEquals(Boolean.FALSE, ArbitraryInstances.get(Boolean.class));
145     assertEquals(Character.valueOf('\0'), ArbitraryInstances.get(char.class));
146     assertEquals(Character.valueOf('\0'), ArbitraryInstances.get(Character.class));
147     assertEquals(Byte.valueOf((byte) 0), ArbitraryInstances.get(byte.class));
148     assertEquals(Byte.valueOf((byte) 0), ArbitraryInstances.get(Byte.class));
149     assertEquals(Short.valueOf((short) 0), ArbitraryInstances.get(short.class));
150     assertEquals(Short.valueOf((short) 0), ArbitraryInstances.get(Short.class));
151     assertEquals(Integer.valueOf(0), ArbitraryInstances.get(int.class));
152     assertEquals(Integer.valueOf(0), ArbitraryInstances.get(Integer.class));
153     assertEquals(Long.valueOf(0), ArbitraryInstances.get(long.class));
154     assertEquals(Long.valueOf(0), ArbitraryInstances.get(Long.class));
155     assertEquals(Float.valueOf(0), ArbitraryInstances.get(float.class));
156     assertEquals(Float.valueOf(0), ArbitraryInstances.get(Float.class));
157     assertEquals(Double.valueOf(0), ArbitraryInstances.get(double.class));
158     assertEquals(Double.valueOf(0), ArbitraryInstances.get(Double.class));
159     assertEquals(UnsignedInteger.ZERO, ArbitraryInstances.get(UnsignedInteger.class));
160     assertEquals(UnsignedLong.ZERO, ArbitraryInstances.get(UnsignedLong.class));
161     assertEquals(0, ArbitraryInstances.get(BigDecimal.class).intValue());
162     assertEquals(0, ArbitraryInstances.get(BigInteger.class).intValue());
163     assertEquals("", ArbitraryInstances.get(String.class));
164     assertEquals("", ArbitraryInstances.get(CharSequence.class));
165     assertEquals(TimeUnit.SECONDS, ArbitraryInstances.get(TimeUnit.class));
166     assertNotNull(ArbitraryInstances.get(Object.class));
167     assertEquals(0, ArbitraryInstances.get(Number.class));
168     assertEquals(Charsets.UTF_8, ArbitraryInstances.get(Charset.class));
169     assertNotNull(ArbitraryInstances.get(UUID.class));
170   }
171 
testGet_collections()172   public void testGet_collections() {
173     assertEquals(ImmutableSet.of().iterator(), ArbitraryInstances.get(Iterator.class));
174     assertFalse(ArbitraryInstances.get(PeekingIterator.class).hasNext());
175     assertFalse(ArbitraryInstances.get(ListIterator.class).hasNext());
176     assertEquals(ImmutableSet.of(), ArbitraryInstances.get(Iterable.class));
177     assertEquals(ImmutableSet.of(), ArbitraryInstances.get(Set.class));
178     assertEquals(ImmutableSet.of(), ArbitraryInstances.get(ImmutableSet.class));
179     assertEquals(ImmutableSortedSet.of(), ArbitraryInstances.get(SortedSet.class));
180     assertEquals(ImmutableSortedSet.of(), ArbitraryInstances.get(ImmutableSortedSet.class));
181     assertEquals(ImmutableList.of(), ArbitraryInstances.get(Collection.class));
182     assertEquals(ImmutableList.of(), ArbitraryInstances.get(ImmutableCollection.class));
183     assertEquals(ImmutableList.of(), ArbitraryInstances.get(List.class));
184     assertEquals(ImmutableList.of(), ArbitraryInstances.get(ImmutableList.class));
185     assertEquals(ImmutableMap.of(), ArbitraryInstances.get(Map.class));
186     assertEquals(ImmutableMap.of(), ArbitraryInstances.get(ImmutableMap.class));
187     assertEquals(ImmutableSortedMap.of(), ArbitraryInstances.get(SortedMap.class));
188     assertEquals(ImmutableSortedMap.of(), ArbitraryInstances.get(ImmutableSortedMap.class));
189     assertEquals(ImmutableMultiset.of(), ArbitraryInstances.get(Multiset.class));
190     assertEquals(ImmutableMultiset.of(), ArbitraryInstances.get(ImmutableMultiset.class));
191     assertTrue(ArbitraryInstances.get(SortedMultiset.class).isEmpty());
192     assertEquals(ImmutableMultimap.of(), ArbitraryInstances.get(Multimap.class));
193     assertEquals(ImmutableMultimap.of(), ArbitraryInstances.get(ImmutableMultimap.class));
194     assertTrue(ArbitraryInstances.get(SortedSetMultimap.class).isEmpty());
195     assertEquals(ImmutableTable.of(), ArbitraryInstances.get(Table.class));
196     assertEquals(ImmutableTable.of(), ArbitraryInstances.get(ImmutableTable.class));
197     assertTrue(ArbitraryInstances.get(RowSortedTable.class).isEmpty());
198     assertEquals(ImmutableBiMap.of(), ArbitraryInstances.get(BiMap.class));
199     assertEquals(ImmutableBiMap.of(), ArbitraryInstances.get(ImmutableBiMap.class));
200     assertTrue(ArbitraryInstances.get(ImmutableClassToInstanceMap.class).isEmpty());
201     assertTrue(ArbitraryInstances.get(ClassToInstanceMap.class).isEmpty());
202     assertTrue(ArbitraryInstances.get(ListMultimap.class).isEmpty());
203     assertTrue(ArbitraryInstances.get(ImmutableListMultimap.class).isEmpty());
204     assertTrue(ArbitraryInstances.get(SetMultimap.class).isEmpty());
205     assertTrue(ArbitraryInstances.get(ImmutableSetMultimap.class).isEmpty());
206     assertTrue(ArbitraryInstances.get(MapDifference.class).areEqual());
207     assertTrue(ArbitraryInstances.get(SortedMapDifference.class).areEqual());
208     assertEquals(Range.all(), ArbitraryInstances.get(Range.class));
209     assertTrue(ArbitraryInstances.get(NavigableSet.class).isEmpty());
210     assertTrue(ArbitraryInstances.get(NavigableMap.class).isEmpty());
211     assertTrue(ArbitraryInstances.get(LinkedList.class).isEmpty());
212     assertTrue(ArbitraryInstances.get(Deque.class).isEmpty());
213     assertTrue(ArbitraryInstances.get(Queue.class).isEmpty());
214     assertTrue(ArbitraryInstances.get(PriorityQueue.class).isEmpty());
215     assertTrue(ArbitraryInstances.get(BitSet.class).isEmpty());
216     assertTrue(ArbitraryInstances.get(TreeSet.class).isEmpty());
217     assertTrue(ArbitraryInstances.get(TreeMap.class).isEmpty());
218     assertFreshInstanceReturned(
219         LinkedList.class,
220         Deque.class,
221         Queue.class,
222         PriorityQueue.class,
223         BitSet.class,
224         TreeSet.class,
225         TreeMap.class);
226   }
227 
testGet_misc()228   public void testGet_misc() {
229     assertNotNull(ArbitraryInstances.get(CharMatcher.class));
230     assertNotNull(ArbitraryInstances.get(Currency.class).getCurrencyCode());
231     assertNotNull(ArbitraryInstances.get(Locale.class));
232     assertNotNull(ArbitraryInstances.get(Joiner.class).join(ImmutableList.of("a")));
233     assertNotNull(ArbitraryInstances.get(Splitter.class).split("a,b"));
234     assertThat(ArbitraryInstances.get(com.google.common.base.Optional.class)).isAbsent();
235     ArbitraryInstances.get(Stopwatch.class).start();
236     assertNotNull(ArbitraryInstances.get(Ticker.class));
237     assertFreshInstanceReturned(Random.class);
238     assertEquals(
239         ArbitraryInstances.get(Random.class).nextInt(),
240         ArbitraryInstances.get(Random.class).nextInt());
241   }
242 
testGet_concurrent()243   public void testGet_concurrent() {
244     assertTrue(ArbitraryInstances.get(BlockingDeque.class).isEmpty());
245     assertTrue(ArbitraryInstances.get(BlockingQueue.class).isEmpty());
246     assertTrue(ArbitraryInstances.get(DelayQueue.class).isEmpty());
247     assertTrue(ArbitraryInstances.get(SynchronousQueue.class).isEmpty());
248     assertTrue(ArbitraryInstances.get(PriorityBlockingQueue.class).isEmpty());
249     assertTrue(ArbitraryInstances.get(ConcurrentMap.class).isEmpty());
250     assertTrue(ArbitraryInstances.get(ConcurrentNavigableMap.class).isEmpty());
251     ArbitraryInstances.get(Executor.class).execute(ArbitraryInstances.get(Runnable.class));
252     assertNotNull(ArbitraryInstances.get(ThreadFactory.class));
253     assertFreshInstanceReturned(
254         BlockingQueue.class,
255         BlockingDeque.class,
256         PriorityBlockingQueue.class,
257         DelayQueue.class,
258         SynchronousQueue.class,
259         ConcurrentMap.class,
260         ConcurrentNavigableMap.class,
261         AtomicReference.class,
262         AtomicBoolean.class,
263         AtomicInteger.class,
264         AtomicLong.class,
265         AtomicDouble.class);
266   }
267 
268   @SuppressWarnings("unchecked") // functor classes have no type parameters
testGet_functors()269   public void testGet_functors() {
270     assertEquals(0, ArbitraryInstances.get(Comparator.class).compare("abc", 123));
271     assertTrue(ArbitraryInstances.get(Predicate.class).apply("abc"));
272     assertTrue(ArbitraryInstances.get(Equivalence.class).equivalent(1, 1));
273     assertFalse(ArbitraryInstances.get(Equivalence.class).equivalent(1, 2));
274   }
275 
276   @SuppressWarnings("SelfComparison")
testGet_comparable()277   public void testGet_comparable() {
278     @SuppressWarnings("unchecked") // The null value can compare with any Object
279     Comparable<Object> comparable = ArbitraryInstances.get(Comparable.class);
280     assertEquals(0, comparable.compareTo(comparable));
281     assertTrue(comparable.compareTo("") > 0);
282     assertThrows(NullPointerException.class, () -> comparable.compareTo(null));
283   }
284 
testGet_array()285   public void testGet_array() {
286     assertThat(ArbitraryInstances.get(int[].class)).isEmpty();
287     assertThat(ArbitraryInstances.get(Object[].class)).isEmpty();
288     assertThat(ArbitraryInstances.get(String[].class)).isEmpty();
289   }
290 
testGet_enum()291   public void testGet_enum() {
292     assertNull(ArbitraryInstances.get(EmptyEnum.class));
293     assertEquals(Direction.UP, ArbitraryInstances.get(Direction.class));
294   }
295 
testGet_interface()296   public void testGet_interface() {
297     assertNull(ArbitraryInstances.get(SomeInterface.class));
298   }
299 
testGet_runnable()300   public void testGet_runnable() {
301     ArbitraryInstances.get(Runnable.class).run();
302   }
303 
testGet_class()304   public void testGet_class() {
305     assertSame(SomeAbstractClass.INSTANCE, ArbitraryInstances.get(SomeAbstractClass.class));
306     assertSame(
307         WithPrivateConstructor.INSTANCE, ArbitraryInstances.get(WithPrivateConstructor.class));
308     assertNull(ArbitraryInstances.get(NoDefaultConstructor.class));
309     assertSame(
310         WithExceptionalConstructor.INSTANCE,
311         ArbitraryInstances.get(WithExceptionalConstructor.class));
312     assertNull(ArbitraryInstances.get(NonPublicClass.class));
313   }
314 
testGet_mutable()315   public void testGet_mutable() {
316     assertEquals(0, ArbitraryInstances.get(ArrayList.class).size());
317     assertEquals(0, ArbitraryInstances.get(HashMap.class).size());
318     assertThat(ArbitraryInstances.get(Appendable.class).toString()).isEmpty();
319     assertThat(ArbitraryInstances.get(StringBuilder.class).toString()).isEmpty();
320     assertThat(ArbitraryInstances.get(StringBuffer.class).toString()).isEmpty();
321     assertFreshInstanceReturned(
322         ArrayList.class,
323         HashMap.class,
324         Appendable.class,
325         StringBuilder.class,
326         StringBuffer.class,
327         Throwable.class,
328         Exception.class);
329   }
330 
testGet_io()331   public void testGet_io() throws IOException {
332     assertEquals(-1, ArbitraryInstances.get(InputStream.class).read());
333     assertEquals(-1, ArbitraryInstances.get(ByteArrayInputStream.class).read());
334     assertEquals(-1, ArbitraryInstances.get(Readable.class).read(CharBuffer.allocate(1)));
335     assertEquals(-1, ArbitraryInstances.get(Reader.class).read());
336     assertEquals(-1, ArbitraryInstances.get(StringReader.class).read());
337     assertEquals(0, ArbitraryInstances.get(Buffer.class).capacity());
338     assertEquals(0, ArbitraryInstances.get(CharBuffer.class).capacity());
339     assertEquals(0, ArbitraryInstances.get(ByteBuffer.class).capacity());
340     assertEquals(0, ArbitraryInstances.get(ShortBuffer.class).capacity());
341     assertEquals(0, ArbitraryInstances.get(IntBuffer.class).capacity());
342     assertEquals(0, ArbitraryInstances.get(LongBuffer.class).capacity());
343     assertEquals(0, ArbitraryInstances.get(FloatBuffer.class).capacity());
344     assertEquals(0, ArbitraryInstances.get(DoubleBuffer.class).capacity());
345     ArbitraryInstances.get(PrintStream.class).println("test");
346     ArbitraryInstances.get(PrintWriter.class).println("test");
347     assertNotNull(ArbitraryInstances.get(File.class));
348     assertFreshInstanceReturned(
349         ByteArrayOutputStream.class, OutputStream.class,
350         Writer.class, StringWriter.class,
351         PrintStream.class, PrintWriter.class);
352     assertEquals(ByteSource.empty(), ArbitraryInstances.get(ByteSource.class));
353     assertEquals(CharSource.empty(), ArbitraryInstances.get(CharSource.class));
354     assertNotNull(ArbitraryInstances.get(ByteSink.class));
355     assertNotNull(ArbitraryInstances.get(CharSink.class));
356   }
357 
testGet_reflect()358   public void testGet_reflect() {
359     assertNotNull(ArbitraryInstances.get(Type.class));
360     assertNotNull(ArbitraryInstances.get(AnnotatedElement.class));
361     assertNotNull(ArbitraryInstances.get(GenericDeclaration.class));
362   }
363 
testGet_regex()364   public void testGet_regex() {
365     assertEquals(Pattern.compile("").pattern(), ArbitraryInstances.get(Pattern.class).pattern());
366     assertEquals(0, ArbitraryInstances.get(MatchResult.class).groupCount());
367   }
368 
testGet_usePublicConstant()369   public void testGet_usePublicConstant() {
370     assertSame(WithPublicConstant.INSTANCE, ArbitraryInstances.get(WithPublicConstant.class));
371   }
372 
testGet_useFirstPublicConstant()373   public void testGet_useFirstPublicConstant() {
374     assertSame(WithPublicConstants.FIRST, ArbitraryInstances.get(WithPublicConstants.class));
375   }
376 
testGet_nullConstantIgnored()377   public void testGet_nullConstantIgnored() {
378     assertSame(FirstConstantIsNull.SECOND, ArbitraryInstances.get(FirstConstantIsNull.class));
379   }
380 
testGet_constantWithGenericsNotUsed()381   public void testGet_constantWithGenericsNotUsed() {
382     assertNull(ArbitraryInstances.get(WithGenericConstant.class));
383   }
384 
testGet_nullConstant()385   public void testGet_nullConstant() {
386     assertNull(ArbitraryInstances.get(WithNullConstant.class));
387   }
388 
testGet_constantTypeDoesNotMatch()389   public void testGet_constantTypeDoesNotMatch() {
390     assertNull(ArbitraryInstances.get(ParentClassHasConstant.class));
391   }
392 
testGet_nonPublicConstantNotUsed()393   public void testGet_nonPublicConstantNotUsed() {
394     assertNull(ArbitraryInstances.get(NonPublicConstantIgnored.class));
395   }
396 
testGet_nonStaticFieldNotUsed()397   public void testGet_nonStaticFieldNotUsed() {
398     assertNull(ArbitraryInstances.get(NonStaticFieldIgnored.class));
399   }
400 
testGet_constructorPreferredOverConstants()401   public void testGet_constructorPreferredOverConstants() {
402     assertNotNull(ArbitraryInstances.get(WithPublicConstructorAndConstant.class));
403     assertTrue(
404         ArbitraryInstances.get(WithPublicConstructorAndConstant.class)
405             != ArbitraryInstances.get(WithPublicConstructorAndConstant.class));
406   }
407 
testGet_nonFinalFieldNotUsed()408   public void testGet_nonFinalFieldNotUsed() {
409     assertNull(ArbitraryInstances.get(NonFinalFieldIgnored.class));
410   }
411 
assertFreshInstanceReturned(Class<?>.... mutableClasses)412   private static void assertFreshInstanceReturned(Class<?>... mutableClasses) {
413     for (Class<?> mutableClass : mutableClasses) {
414       Object instance = ArbitraryInstances.get(mutableClass);
415       assertNotNull("Expected to return non-null for: " + mutableClass, instance);
416       assertNotSame(
417           "Expected to return fresh instance for: " + mutableClass,
418           instance,
419           ArbitraryInstances.get(mutableClass));
420     }
421   }
422 
423   private enum EmptyEnum {}
424 
425   private enum Direction {
426     UP,
427     DOWN
428   }
429 
430   public interface SomeInterface {}
431 
432   public abstract static class SomeAbstractClass {
433     public static final SomeAbstractClass INSTANCE = new SomeAbstractClass() {};
434 
SomeAbstractClass()435     public SomeAbstractClass() {}
436   }
437 
438   static class NonPublicClass {
NonPublicClass()439     public NonPublicClass() {}
440   }
441 
442   private static class WithPrivateConstructor {
443     public static final WithPrivateConstructor INSTANCE = new WithPrivateConstructor();
444   }
445 
446   public static class NoDefaultConstructor {
NoDefaultConstructor(@uppressWarnings"unused") int i)447     public NoDefaultConstructor(@SuppressWarnings("unused") int i) {}
448   }
449 
450   public static class WithExceptionalConstructor {
451     public static final WithExceptionalConstructor INSTANCE =
452         new WithExceptionalConstructor("whatever");
453 
WithExceptionalConstructor()454     public WithExceptionalConstructor() {
455       throw new RuntimeException();
456     }
457 
WithExceptionalConstructor(String unused)458     private WithExceptionalConstructor(String unused) {}
459   }
460 
461   private static class WithPublicConstant {
462     public static final WithPublicConstant INSTANCE = new WithPublicConstant();
463   }
464 
465   private static class ParentClassHasConstant extends WithPublicConstant {}
466 
467   public static class WithGenericConstant<T> {
468     public static final WithGenericConstant<String> STRING_CONSTANT = new WithGenericConstant<>();
469 
WithGenericConstant()470     private WithGenericConstant() {}
471   }
472 
473   public static class WithNullConstant {
474     public static final @Nullable WithNullConstant NULL = null;
475 
WithNullConstant()476     private WithNullConstant() {}
477   }
478 
479   public static class WithPublicConstructorAndConstant {
480     public static final WithPublicConstructorAndConstant INSTANCE =
481         new WithPublicConstructorAndConstant();
482 
WithPublicConstructorAndConstant()483     public WithPublicConstructorAndConstant() {}
484   }
485 
486   private static class WithPublicConstants {
487     public static final WithPublicConstants FIRST = new WithPublicConstants();
488 
489     // To test that we pick the first constant alphabetically
490     @SuppressWarnings("unused")
491     public static final WithPublicConstants SECOND = new WithPublicConstants();
492   }
493 
494   private static class FirstConstantIsNull {
495     // To test that null constant is ignored
496     @SuppressWarnings("unused")
497     public static final @Nullable FirstConstantIsNull FIRST = null;
498 
499     public static final FirstConstantIsNull SECOND = new FirstConstantIsNull();
500   }
501 
502   public static class NonFinalFieldIgnored {
503     public static NonFinalFieldIgnored instance = new NonFinalFieldIgnored();
504 
NonFinalFieldIgnored()505     private NonFinalFieldIgnored() {}
506   }
507 
508   public static class NonPublicConstantIgnored {
509     static final NonPublicConstantIgnored INSTANCE = new NonPublicConstantIgnored();
510 
NonPublicConstantIgnored()511     private NonPublicConstantIgnored() {}
512   }
513 
514   public static class NonStaticFieldIgnored {
515     // This should cause infinite recursion. But it shouldn't be used anyway.
516     public final NonStaticFieldIgnored instance = new NonStaticFieldIgnored();
517 
NonStaticFieldIgnored()518     private NonStaticFieldIgnored() {}
519   }
520 }
521