/*
* Copyright (C) 2012 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.testing;
import static com.google.common.base.Preconditions.checkArgument;
import com.google.common.annotations.Beta;
import com.google.common.base.CharMatcher;
import com.google.common.base.Charsets;
import com.google.common.base.Defaults;
import com.google.common.base.Equivalence;
import com.google.common.base.Joiner;
import com.google.common.base.Optional;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.base.Splitter;
import com.google.common.base.Ticker;
import com.google.common.collect.BiMap;
import com.google.common.collect.ClassToInstanceMap;
import com.google.common.collect.Constraint;
import com.google.common.collect.Constraints;
import com.google.common.collect.ImmutableBiMap;
import com.google.common.collect.ImmutableClassToInstanceMap;
import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableListMultimap;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.ImmutableMultiset;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ImmutableSetMultimap;
import com.google.common.collect.ImmutableSortedMap;
import com.google.common.collect.ImmutableSortedSet;
import com.google.common.collect.ImmutableTable;
import com.google.common.collect.Iterators;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.MapConstraint;
import com.google.common.collect.MapConstraints;
import com.google.common.collect.MapDifference;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import com.google.common.collect.Multimaps;
import com.google.common.collect.Multiset;
import com.google.common.collect.Multisets;
import com.google.common.collect.Ordering;
import com.google.common.collect.PeekingIterator;
import com.google.common.collect.Range;
import com.google.common.collect.Ranges;
import com.google.common.collect.RowSortedTable;
import com.google.common.collect.SetMultimap;
import com.google.common.collect.Sets;
import com.google.common.collect.SortedMapDifference;
import com.google.common.collect.SortedMultiset;
import com.google.common.collect.SortedSetMultimap;
import com.google.common.collect.Table;
import com.google.common.collect.Tables;
import com.google.common.collect.TreeBasedTable;
import com.google.common.collect.TreeMultimap;
import com.google.common.collect.TreeMultiset;
import com.google.common.primitives.Primitives;
import com.google.common.primitives.UnsignedInteger;
import com.google.common.primitives.UnsignedLong;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.GenericDeclaration;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;
import java.lang.reflect.Type;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.nio.Buffer;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.DoubleBuffer;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import java.nio.LongBuffer;
import java.nio.ShortBuffer;
import java.nio.charset.Charset;
import java.util.ArrayDeque;
import java.util.Collection;
import java.util.Comparator;
import java.util.Currency;
import java.util.Deque;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.NavigableSet;
import java.util.Queue;
import java.util.Random;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.concurrent.BlockingDeque;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentNavigableMap;
import java.util.concurrent.ConcurrentSkipListMap;
import java.util.concurrent.Executor;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.regex.MatchResult;
import java.util.regex.Pattern;
import javax.annotation.Nullable;
/**
* Supplies an arbitrary "default" instance for a wide range of types, often useful in testing
* utilities.
*
* <p>Covers common types defined in {@code java.lang}, {@code java.lang.reflect}, {@code java.io},
* {@code java.nio}, {@code java.math}, {@code java.util}, {@code java.util.concurrent},
* {@code java.util.regex}, {@code com.google.common.base}, {@code com.google.common.collect}
* and {@code com.google.common.primitives}. In addition, any public class that exposes a public
* parameter-less constructor will be "new"d and returned.
*
* <p>All default instances returned by {@link #get} are generics-safe. Clients won't get type
* errors for using {@code get(Comparator.class)} as a {@code Comparator<Foo>}, for example.
* Immutable empty instances are returned for collection types; {@code ""} for string;
* {@code 0} for number types; reasonable default instance for other stateless types. For mutable
* types, a fresh instance is created each time {@code get()} is called.
*
* @author Kevin Bourrillion
* @author Ben Yu
* @since 12.0
*/
@Beta
public final class ArbitraryInstances {
// Compare by toString() to satisfy 2 properties:
// 1. compareTo(null) should throw NullPointerException
// 2. the order is deterministic and easy to understand, for debugging purpose.
private static final Comparable<Object> BY_TO_STRING = new Comparable<Object>() {
@Override public int compareTo(Object o) {
return toString().compareTo(o.toString());
}
@Override public String toString() {
return "BY_TO_STRING";
}
};
// Always equal is a valid total ordering. And it works for any Object.
private static final Ordering<Object> ALWAYS_EQUAL = new Ordering<Object>() {
@Override public int compare(Object o1, Object o2) {
return 0;
}
@Override public String toString() {
return "ALWAYS_EQUAL";
}
};
private static final ClassToInstanceMap<Object> DEFAULTS = ImmutableClassToInstanceMap.builder()
// primitives
.put(Number.class, 0)
.put(UnsignedInteger.class, UnsignedInteger.ZERO)
.put(UnsignedLong.class, UnsignedLong.ZERO)
.put(BigInteger.class, BigInteger.ZERO)
.put(BigDecimal.class, BigDecimal.ZERO)
.put(CharSequence.class, "")
.put(String.class, "")
.put(Pattern.class, Pattern.compile(""))
.put(MatchResult.class, Pattern.compile("").matcher("").toMatchResult())
.put(TimeUnit.class, TimeUnit.SECONDS)
.put(Charset.class, Charsets.UTF_8)
.put(Currency.class, Currency.getInstance(Locale.US))
.put(Locale.class, Locale.US)
// common.base
.put(CharMatcher.class, CharMatcher.NONE)
.put(Joiner.class, Joiner.on(','))
.put(Splitter.class, Splitter.on(','))
.put(Optional.class, Optional.absent())
.put(Predicate.class, Predicates.alwaysTrue())
.put(Equivalence.class, Equivalence.equals())
.put(Ticker.class, Ticker.systemTicker())
// io types
.put(InputStream.class, new ByteArrayInputStream(new byte[0]))
.put(ByteArrayInputStream.class, new ByteArrayInputStream(new byte[0]))
.put(Readable.class, new StringReader(""))
.put(Reader.class, new StringReader(""))
.put(StringReader.class, new StringReader(""))
.put(Buffer.class, ByteBuffer.allocate(0))
.put(CharBuffer.class, CharBuffer.allocate(0))
.put(ByteBuffer.class, ByteBuffer.allocate(0))
.put(ShortBuffer.class, ShortBuffer.allocate(0))
.put(IntBuffer.class, IntBuffer.allocate(0))
.put(LongBuffer.class, LongBuffer.allocate(0))
.put(FloatBuffer.class, FloatBuffer.allocate(0))
.put(DoubleBuffer.class, DoubleBuffer.allocate(0))
.put(File.class, new File(""))
// All collections are immutable empty. So safe for any type parameter.
.put(Iterator.class, Iterators.emptyIterator())
.put(PeekingIterator.class, Iterators.peekingIterator(Iterators.emptyIterator()))
.put(ListIterator.class, ImmutableList.of().listIterator())
.put(Iterable.class, ImmutableSet.of())
.put(Collection.class, ImmutableList.of())
.put(ImmutableCollection.class, ImmutableList.of())
.put(List.class, ImmutableList.of())
.put(ImmutableList.class, ImmutableList.of())
.put(Set.class, ImmutableSet.of())
.put(ImmutableSet.class, ImmutableSet.of())
.put(SortedSet.class, ImmutableSortedSet.of())
.put(ImmutableSortedSet.class, ImmutableSortedSet.of())
.put(NavigableSet.class, Sets.unmodifiableNavigableSet(Sets.newTreeSet()))
.put(Map.class, ImmutableMap.of())
.put(ImmutableMap.class, ImmutableMap.of())
.put(SortedMap.class, ImmutableSortedMap.of())
.put(ImmutableSortedMap.class, ImmutableSortedMap.of())
.put(NavigableMap.class, Maps.unmodifiableNavigableMap(Maps.newTreeMap()))
.put(Multimap.class, ImmutableMultimap.of())
.put(ImmutableMultimap.class, ImmutableMultimap.of())
.put(ListMultimap.class, ImmutableListMultimap.of())
.put(ImmutableListMultimap.class, ImmutableListMultimap.of())
.put(SetMultimap.class, ImmutableSetMultimap.of())
.put(ImmutableSetMultimap.class, ImmutableSetMultimap.of())
.put(SortedSetMultimap.class, Multimaps.unmodifiableSortedSetMultimap(TreeMultimap.create()))
.put(Multiset.class, ImmutableMultiset.of())
.put(ImmutableMultiset.class, ImmutableMultiset.of())
.put(SortedMultiset.class, Multisets.unmodifiableSortedMultiset(TreeMultiset.create()))
.put(BiMap.class, ImmutableBiMap.of())
.put(ImmutableBiMap.class, ImmutableBiMap.of())
.put(Table.class, ImmutableTable.of())
.put(ImmutableTable.class, ImmutableTable.of())
.put(RowSortedTable.class, Tables.unmodifiableRowSortedTable(TreeBasedTable.create()))
.put(ClassToInstanceMap.class, ImmutableClassToInstanceMap.builder().build())
.put(ImmutableClassToInstanceMap.class, ImmutableClassToInstanceMap.builder().build())
.put(Comparable.class, BY_TO_STRING)
.put(Comparator.class, ALWAYS_EQUAL)
.put(Ordering.class, ALWAYS_EQUAL)
.put(Range.class, Ranges.all())
.put(Constraint.class, Constraints.notNull())
.put(MapConstraint.class, MapConstraints.notNull())
.put(MapDifference.class, Maps.difference(ImmutableMap.of(), ImmutableMap.of()))
.put(SortedMapDifference.class,
Maps.difference(ImmutableSortedMap.of(), ImmutableSortedMap.of()))
// reflect
.put(AnnotatedElement.class, Object.class)
.put(GenericDeclaration.class, Object.class)
.put(Type.class, Object.class)
// concurrent
.put(Runnable.class, new Runnable() {
@Override public void run() {}
})
.put(ThreadFactory.class, new ThreadFactory() {
@Override public Thread newThread(Runnable r) {
return new Thread(r);
}
})
.put(Executor.class, new Executor() {
@Override public void execute(Runnable command) {}
})
.build();
/**
* type -> implementation. Inherently mutable interfaces and abstract classes are mapped to their
* default implementations and are "new"d upon get().
*/
private static final ConcurrentMap<Class<?>, Class<?>> implementations = Maps.newConcurrentMap();
private static <T> void setImplementation(Class<T> type, Class<? extends T> implementation) {
checkArgument(type != implementation, "Don't register %s to itself!", type);
checkArgument(!DEFAULTS.containsKey(type),
"A default value was already registered for %s", type);
checkArgument(implementations.put(type, implementation) == null,
"Implementation for %s was already registered", type);
}
static {
setImplementation(Appendable.class, StringBuilder.class);
setImplementation(Queue.class, ArrayDeque.class);
setImplementation(Deque.class, ArrayDeque.class);
setImplementation(BlockingQueue.class, LinkedBlockingDeque.class);
setImplementation(BlockingDeque.class, LinkedBlockingDeque.class);
setImplementation(ConcurrentMap.class, ConcurrentHashMap.class);
setImplementation(ConcurrentNavigableMap.class, ConcurrentSkipListMap.class);
setImplementation(OutputStream.class, ByteArrayOutputStream.class);
setImplementation(Writer.class, StringWriter.class);
setImplementation(PrintStream.class, Mutable.InMemoryPrintStream.class);
setImplementation(PrintWriter.class, Mutable.InMemoryPrintWriter.class);
setImplementation(Random.class, Mutable.DeterministicRandom.class);
}
@SuppressWarnings("unchecked") // it's a subtype map
@Nullable
private static <T> Class<? extends T> getImplementation(Class<T> type) {
return (Class<? extends T>) implementations.get(type);
}
private static final Logger logger = Logger.getLogger(ArbitraryInstances.class.getName());
/**
* Returns an arbitrary value for {@code type} as the null value, or {@code null} if empty-ness is
* unknown for the type.
*/
@Nullable public static <T> T get(Class<T> type) {
T defaultValue = DEFAULTS.getInstance(type);
if (defaultValue != null) {
return defaultValue;
}
Class<? extends T> implementation = getImplementation(type);
if (implementation != null) {
return get(implementation);
}
if (type.isEnum()) {
T[] enumConstants = type.getEnumConstants();
return (enumConstants.length == 0)
? null
: enumConstants[0];
}
if (type.isArray()) {
return createEmptyArray(type);
}
T jvmDefault = Defaults.defaultValue(Primitives.unwrap(type));
if (jvmDefault != null) {
return jvmDefault;
}
if (Modifier.isAbstract(type.getModifiers()) || !Modifier.isPublic(type.getModifiers())) {
return null;
}
final Constructor<T> constructor;
try {
constructor = type.getConstructor();
} catch (NoSuchMethodException e) {
return null;
}
constructor.setAccessible(true); // accessibility check is too slow
try {
return constructor.newInstance();
} catch (InstantiationException impossible) {
throw new AssertionError(impossible);
} catch (IllegalAccessException impossible) {
throw new AssertionError(impossible);
} catch (InvocationTargetException e) {
logger.log(Level.WARNING, "Exception while invoking default constructor.", e.getCause());
return null;
}
}
@SuppressWarnings("unchecked") // same component type means same array type
private static <T> T createEmptyArray(Class<T> arrayType) {
return (T) Array.newInstance(arrayType.getComponentType(), 0);
}
// Internal implementations for mutable types, with public default constructor that get() needs.
private static final class Mutable {
public static final class InMemoryPrintStream extends PrintStream {
public InMemoryPrintStream() {
super(new ByteArrayOutputStream());
}
}
public static final class InMemoryPrintWriter extends PrintWriter {
public InMemoryPrintWriter() {
super(new StringWriter());
}
}
public static final class DeterministicRandom extends Random {
@SuppressWarnings("unused") // invoked by reflection
public DeterministicRandom() {
super(0);
}
}
}
private ArbitraryInstances() {}
}