Package com.google.common.testing

Class ArbitraryInstances

java.lang.Object

com.google.common.testing.ArbitraryInstances

@Beta
@GwtIncompatible
public final class ArbitraryInstances
extends java.lang.Object

Supplies an arbitrary "default" instance for a wide range of types, often useful in testing utilities.

Covers arrays, enums and common types defined in java.lang, java.lang.reflect, java.io, java.nio, java.math, java.util, java.util.concurrent, java.util.regex, com.google.common.base, com.google.common.collect and com.google.common.primitives. In addition, if the type exposes at least one public static final constant of the same type, one of the constants will be used; or if the class exposes a public parameter-less constructor then it will be "new"d and returned.

All default instances returned by get(java.lang.Class<T>) are generics-safe. Clients won't get type errors for using get(Comparator.class) as a Comparator<Foo>, for example. Immutable empty instances are returned for collection types; "" for string; 0 for number types; reasonable default instance for other stateless types. For mutable types, a fresh instance is created each time get() is called.

Since:

12.0

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	ArbitraryInstances.AlwaysEqual
private static class	ArbitraryInstances.ByToString
private static class	ArbitraryInstances.Dummies
private static class	ArbitraryInstances.NullByteSink

Field Summary

Fields

Modifier and Type	Field	Description
private static Ordering<java.lang.reflect.Field>	BY_FIELD_NAME
private static ClassToInstanceMap<java.lang.Object>	DEFAULTS
private static java.util.concurrent.ConcurrentMap<java.lang.Class<?>,java.lang.Class<?>>	implementations	type → implementation.
private static java.util.logging.Logger	logger

Constructor Summary

Constructors

Modifier	Constructor	Description
private	ArbitraryInstances()

Method Summary

Modifier and Type	Method	Description
private static <T> T	arbitraryConstantInstanceOrNull(java.lang.Class<T> type)
private static <T> T	createEmptyArray(java.lang.Class<T> arrayType)
static <T> T	get(java.lang.Class<T> type)	Returns an arbitrary instance for type, or null if no arbitrary instance can be determined.
private static <T> java.lang.Class<? extends T>	getImplementation(java.lang.Class<T> type)
private static java.util.regex.MatchResult	newMatchResult()	Returns a new MatchResult that corresponds to a successful match.
private static <T> void	setImplementation(java.lang.Class<T> type, java.lang.Class<? extends T> implementation)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

BY_FIELD_NAME

private static final Ordering<java.lang.reflect.Field> BY_FIELD_NAME

DEFAULTS

private static final ClassToInstanceMap<java.lang.Object> DEFAULTS

implementations

private static final java.util.concurrent.ConcurrentMap<java.lang.Class<?>,java.lang.Class<?>> implementations

type → implementation. Inherently mutable interfaces and abstract classes are mapped to their default implementations and are "new"d upon get().

logger

private static final java.util.logging.Logger logger

Constructor Detail

ArbitraryInstances

private ArbitraryInstances()

Method Detail

newMatchResult

private static java.util.regex.MatchResult newMatchResult()

Returns a new MatchResult that corresponds to a successful match. Apache Harmony (used in Android) requires a successful match in order to generate a MatchResult: http://goo.gl/5VQFmC

setImplementation

private static <T> void setImplementation(java.lang.Class<T> type,
                                          java.lang.Class<? extends T> implementation)

getImplementation

private static <T> java.lang.Class<? extends T> getImplementation(java.lang.Class<T> type)

get

public static <T> T get(java.lang.Class<T> type)

Returns an arbitrary instance for type, or null if no arbitrary instance can be determined.

arbitraryConstantInstanceOrNull

private static <T> T arbitraryConstantInstanceOrNull(java.lang.Class<T> type)

createEmptyArray

private static <T> T createEmptyArray(java.lang.Class<T> arrayType)