com.google.common.base
Class Predicates

java.lang.Object
  com.google.common.base.Predicates

@GwtCompatible(emulated=true)
public final class Predicates
extends Object

Static utility methods pertaining to Predicate instances.

All methods returns serializable predicates as long as they're given serializable parameters.

Since:

2.0 (imported from Google Collections Library)

Author:

Kevin Bourrillion

Method Summary

static <T> Predicate<T>	alwaysFalse() Returns a predicate that always evaluates to false.
static <T> Predicate<T>	alwaysTrue() Returns a predicate that always evaluates to true.
static <T> Predicate<T>	and(Iterable<? extends Predicate<? super T>> components) Returns a predicate that evaluates to true if each of its components evaluates to true.
static <T> Predicate<T>	and(Predicate<? super T>... components) Returns a predicate that evaluates to true if each of its components evaluates to true.
static <T> Predicate<T>	and(Predicate<? super T> first, Predicate<? super T> second) Returns a predicate that evaluates to true if both of its components evaluate to true.
static Predicate<Class<?>>	assignableFrom(Class<?> clazz) Returns a predicate that evaluates to true if the class being tested is assignable from the given class.
static <A,B> Predicate<A>	compose(Predicate<B> predicate, Function<A,? extends B> function) Returns the composition of a function and a predicate.
static Predicate<CharSequence>	contains(Pattern pattern) Returns a predicate that evaluates to true if the CharSequence being tested contains any match for the given regular expression pattern.
static Predicate<CharSequence>	containsPattern(String pattern) Returns a predicate that evaluates to true if the CharSequence being tested contains any match for the given regular expression pattern.
static <T> Predicate<T>	equalTo(T target) Returns a predicate that evaluates to true if the object being tested equals() the given target or both are null.
static <T> Predicate<T>	in(Collection<? extends T> target) Returns a predicate that evaluates to true if the object reference being tested is a member of the given collection.
static Predicate<Object>	instanceOf(Class<?> clazz) Returns a predicate that evaluates to true if the object being tested is an instance of the given class.
static <T> Predicate<T>	isNull() Returns a predicate that evaluates to true if the object reference being tested is null.
static <T> Predicate<T>	not(Predicate<T> predicate) Returns a predicate that evaluates to true if the given predicate evaluates to false.
static <T> Predicate<T>	notNull() Returns a predicate that evaluates to true if the object reference being tested is not null.
static <T> Predicate<T>	or(Iterable<? extends Predicate<? super T>> components) Returns a predicate that evaluates to true if any one of its components evaluates to true.
static <T> Predicate<T>	or(Predicate<? super T>... components) Returns a predicate that evaluates to true if any one of its components evaluates to true.
static <T> Predicate<T>	or(Predicate<? super T> first, Predicate<? super T> second) Returns a predicate that evaluates to true if either of its components evaluates to true.

Methods inherited from class java.lang.Object

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

Method Detail

alwaysTrue

@GwtCompatible(serializable=true)
public static <T> Predicate<T> alwaysTrue()

Returns a predicate that always evaluates to true.

alwaysFalse

@GwtCompatible(serializable=true)
public static <T> Predicate<T> alwaysFalse()

Returns a predicate that always evaluates to false.

isNull

@GwtCompatible(serializable=true)
public static <T> Predicate<T> isNull()

Returns a predicate that evaluates to true if the object reference being tested is null.

notNull

@GwtCompatible(serializable=true)
public static <T> Predicate<T> notNull()

Returns a predicate that evaluates to true if the object reference being tested is not null.

not

public static <T> Predicate<T> not(Predicate<T> predicate)

Returns a predicate that evaluates to true if the given predicate evaluates to false.

and

public static <T> Predicate<T> and(Iterable<? extends Predicate<? super T>> components)

Returns a predicate that evaluates to true if each of its components evaluates to true. The components are evaluated in order, and evaluation will be "short-circuited" as soon as a false predicate is found. It defensively copies the iterable passed in, so future changes to it won't alter the behavior of this predicate. If components is empty, the returned predicate will always evaluate to true.

and

public static <T> Predicate<T> and(Predicate<? super T>... components)

Returns a predicate that evaluates to true if each of its components evaluates to true. The components are evaluated in order, and evaluation will be "short-circuited" as soon as a false predicate is found. It defensively copies the array passed in, so future changes to it won't alter the behavior of this predicate. If components is empty, the returned predicate will always evaluate to true.

and

public static <T> Predicate<T> and(Predicate<? super T> first,
                                   Predicate<? super T> second)

Returns a predicate that evaluates to true if both of its components evaluate to true. The components are evaluated in order, and evaluation will be "short-circuited" as soon as a false predicate is found.

or

public static <T> Predicate<T> or(Iterable<? extends Predicate<? super T>> components)

Returns a predicate that evaluates to true if any one of its components evaluates to true. The components are evaluated in order, and evaluation will be "short-circuited" as soon as a true predicate is found. It defensively copies the iterable passed in, so future changes to it won't alter the behavior of this predicate. If components is empty, the returned predicate will always evaluate to false.

or

public static <T> Predicate<T> or(Predicate<? super T>... components)

Returns a predicate that evaluates to true if any one of its components evaluates to true. The components are evaluated in order, and evaluation will be "short-circuited" as soon as a true predicate is found. It defensively copies the array passed in, so future changes to it won't alter the behavior of this predicate. If components is empty, the returned predicate will always evaluate to false.

or

public static <T> Predicate<T> or(Predicate<? super T> first,
                                  Predicate<? super T> second)

Returns a predicate that evaluates to true if either of its components evaluates to true. The components are evaluated in order, and evaluation will be "short-circuited" as soon as a true predicate is found.

equalTo

public static <T> Predicate<T> equalTo(@Nullable
                                       T target)

Returns a predicate that evaluates to true if the object being tested equals() the given target or both are null.

instanceOf

@GwtIncompatible(value="Class.isInstance")
public static Predicate<Object> instanceOf(Class<?> clazz)

Returns a predicate that evaluates to true if the object being tested is an instance of the given class. If the object being tested is null this predicate evaluates to false.

If you want to filter an Iterable to narrow its type, consider using Iterables.filter(Iterable, Class) in preference.

Warning: contrary to the typical assumptions about predicates (as documented at Predicate.apply(T)), the returned predicate may not be consistent with equals. For example, instanceOf(ArrayList.class) will yield different results for the two equal instances Lists.newArrayList(1) and Arrays.asList(1).

assignableFrom

@GwtIncompatible(value="Class.isAssignableFrom")
@Beta
public static Predicate<Class<?>> assignableFrom(Class<?> clazz)

Returns a predicate that evaluates to true if the class being tested is assignable from the given class. The returned predicate does not allow null inputs.

Since:

10.0

in

public static <T> Predicate<T> in(Collection<? extends T> target)

Returns a predicate that evaluates to true if the object reference being tested is a member of the given collection. It does not defensively copy the collection passed in, so future changes to it will alter the behavior of the predicate.

This method can technically accept any Collection<?>, but using a typed collection helps prevent bugs. This approach doesn't block any potential users since it is always possible to use Predicates.<Object>in().

Parameters:

target - the collection that may contain the function input

compose

public static <A,B> Predicate<A> compose(Predicate<B> predicate,
                                         Function<A,? extends B> function)

Returns the composition of a function and a predicate. For every x, the generated predicate returns predicate(function(x)).

Returns:

the composition of the provided function and predicate

containsPattern

@GwtIncompatible(value="java.util.regex.Pattern")
public static Predicate<CharSequence> containsPattern(String pattern)

Returns a predicate that evaluates to true if the CharSequence being tested contains any match for the given regular expression pattern. The test used is equivalent to Pattern.compile(pattern).matcher(arg).find()

Throws:

PatternSyntaxException - if the pattern is invalid

Since:

3.0

contains

@GwtIncompatible(value="java.util.regex.Pattern")
public static Predicate<CharSequence> contains(Pattern pattern)

Returns a predicate that evaluates to true if the CharSequence being tested contains any match for the given regular expression pattern. The test used is equivalent to regex.matcher(arg).find()

Since:

3.0