/*
* Copyright (C) 2007 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.base;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.regex.Pattern;
import javax.annotation.Nullable;
/**
* Static utility methods pertaining to {@code Predicate} instances.
*
* <p>All methods returns serializable predicates as long as they're given
* serializable parameters.
*
* <p>See the Guava User Guide article on <a href=
* "http://code.google.com/p/guava-libraries/wiki/FunctionalExplained">the
* use of {@code Predicate}</a>.
*
* @author Kevin Bourrillion
* @since 2.0 (imported from Google Collections Library)
*/
@GwtCompatible(emulated = true)
public final class Predicates {
private Predicates() {}
// TODO(kevinb): considering having these implement a VisitablePredicate
// interface which specifies an accept(PredicateVisitor) method.
/**
* Returns a predicate that always evaluates to {@code true}.
*/
@GwtCompatible(serializable = true)
public static <T> Predicate<T> alwaysTrue() {
return ObjectPredicate.ALWAYS_TRUE.withNarrowedType();
}
/**
* Returns a predicate that always evaluates to {@code false}.
*/
@GwtCompatible(serializable = true)
public static <T> Predicate<T> alwaysFalse() {
return ObjectPredicate.ALWAYS_FALSE.withNarrowedType();
}
/**
* Returns a predicate that evaluates to {@code true} if the object reference
* being tested is null.
*/
@GwtCompatible(serializable = true)
public static <T> Predicate<T> isNull() {
return ObjectPredicate.IS_NULL.withNarrowedType();
}
/**
* Returns a predicate that evaluates to {@code true} if the object reference
* being tested is not null.
*/
@GwtCompatible(serializable = true)
public static <T> Predicate<T> notNull() {
return ObjectPredicate.NOT_NULL.withNarrowedType();
}
/**
* Returns a predicate that evaluates to {@code true} if the given predicate
* evaluates to {@code false}.
*/
public static <T> Predicate<T> not(Predicate<T> predicate) {
return new NotPredicate<T>(predicate);
}
/**
* Returns a predicate that evaluates to {@code true} if each of its
* components evaluates to {@code 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 {@code
* components} is empty, the returned predicate will always evaluate to {@code
* true}.
*/
public static <T> Predicate<T> and(
Iterable<? extends Predicate<? super T>> components) {
return new AndPredicate<T>(defensiveCopy(components));
}
/**
* Returns a predicate that evaluates to {@code true} if each of its
* components evaluates to {@code 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 {@code
* components} is empty, the returned predicate will always evaluate to {@code
* true}.
*/
public static <T> Predicate<T> and(Predicate<? super T>... components) {
return new AndPredicate<T>(defensiveCopy(components));
}
/**
* Returns a predicate that evaluates to {@code true} if both of its
* components evaluate to {@code true}. The components are evaluated in
* order, and evaluation will be "short-circuited" as soon as a false
* predicate is found.
*/
public static <T> Predicate<T> and(Predicate<? super T> first,
Predicate<? super T> second) {
return new AndPredicate<T>(Predicates.<T>asList(
checkNotNull(first), checkNotNull(second)));
}
/**
* Returns a predicate that evaluates to {@code true} if any one of its
* components evaluates to {@code 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 {@code
* components} is empty, the returned predicate will always evaluate to {@code
* false}.
*/
public static <T> Predicate<T> or(
Iterable<? extends Predicate<? super T>> components) {
return new OrPredicate<T>(defensiveCopy(components));
}
/**
* Returns a predicate that evaluates to {@code true} if any one of its
* components evaluates to {@code 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 {@code
* components} is empty, the returned predicate will always evaluate to {@code
* false}.
*/
public static <T> Predicate<T> or(Predicate<? super T>... components) {
return new OrPredicate<T>(defensiveCopy(components));
}
/**
* Returns a predicate that evaluates to {@code true} if either of its
* components evaluates to {@code true}. The components are evaluated in
* order, and evaluation will be "short-circuited" as soon as a
* true predicate is found.
*/
public static <T> Predicate<T> or(
Predicate<? super T> first, Predicate<? super T> second) {
return new OrPredicate<T>(Predicates.<T>asList(
checkNotNull(first), checkNotNull(second)));
}
/**
* Returns a predicate that evaluates to {@code true} if the object being
* tested {@code equals()} the given target or both are null.
*/
public static <T> Predicate<T> equalTo(@Nullable T target) {
return (target == null)
? Predicates.<T>isNull()
: new IsEqualToPredicate<T>(target);
}
/**
* Returns a predicate that evaluates to {@code true} if the object being
* tested is an instance of the given class. If the object being tested
* is {@code null} this predicate evaluates to {@code false}.
*
* <p>If you want to filter an {@code Iterable} to narrow its type, consider
* using {@link com.google.common.collect.Iterables#filter(Iterable, Class)}
* in preference.
*
* <p><b>Warning:</b> contrary to the typical assumptions about predicates (as
* documented at {@link Predicate#apply}), the returned predicate may not be
* <i>consistent with equals</i>. For example, {@code
* instanceOf(ArrayList.class)} will yield different results for the two equal
* instances {@code Lists.newArrayList(1)} and {@code Arrays.asList(1)}.
*/
@GwtIncompatible("Class.isInstance")
public static Predicate<Object> instanceOf(Class<?> clazz) {
return new InstanceOfPredicate(clazz);
}
/**
* Returns a predicate that evaluates to {@code true} if the class being
* tested is assignable from the given class. The returned predicate
* does not allow null inputs.
*
* @since 10.0
*/
@GwtIncompatible("Class.isAssignableFrom")
@Beta
public static Predicate<Class<?>> assignableFrom(Class<?> clazz) {
return new AssignableFromPredicate(clazz);
}
/**
* Returns a predicate that evaluates to {@code 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.
*
* <p>This method can technically accept any {@code Collection<?>}, but using
* a typed collection helps prevent bugs. This approach doesn't block any
* potential users since it is always possible to use {@code
* Predicates.<Object>in()}.
*
* @param target the collection that may contain the function input
*/
public static <T> Predicate<T> in(Collection<? extends T> target) {
return new InPredicate<T>(target);
}
/**
* Returns the composition of a function and a predicate. For every {@code x},
* the generated predicate returns {@code predicate(function(x))}.
*
* @return the composition of the provided function and predicate
*/
public static <A, B> Predicate<A> compose(
Predicate<B> predicate, Function<A, ? extends B> function) {
return new CompositionPredicate<A, B>(predicate, function);
}
/**
* Returns a predicate that evaluates to {@code true} if the
* {@code CharSequence} being tested contains any match for the given
* regular expression pattern. The test used is equivalent to
* {@code Pattern.compile(pattern).matcher(arg).find()}
*
* @throws java.util.regex.PatternSyntaxException if the pattern is invalid
* @since 3.0
*/
@GwtIncompatible(value = "java.util.regex.Pattern")
public static Predicate<CharSequence> containsPattern(String pattern) {
return new ContainsPatternFromStringPredicate(pattern);
}
/**
* Returns a predicate that evaluates to {@code true} if the
* {@code CharSequence} being tested contains any match for the given
* regular expression pattern. The test used is equivalent to
* {@code pattern.matcher(arg).find()}
*
* @since 3.0
*/
@GwtIncompatible(value = "java.util.regex.Pattern")
public static Predicate<CharSequence> contains(Pattern pattern) {
return new ContainsPatternPredicate(pattern);
}
// End public API, begin private implementation classes.
// Package private for GWT serialization.
enum ObjectPredicate implements Predicate<Object> {
/** @see Predicates#alwaysTrue() */
ALWAYS_TRUE {
@Override public boolean apply(@Nullable Object o) {
return true;
}
@Override public String toString() {
return "Predicates.alwaysTrue()";
}
},
/** @see Predicates#alwaysFalse() */
ALWAYS_FALSE {
@Override public boolean apply(@Nullable Object o) {
return false;
}
@Override public String toString() {
return "Predicates.alwaysFalse()";
}
},
/** @see Predicates#isNull() */
IS_NULL {
@Override public boolean apply(@Nullable Object o) {
return o == null;
}
@Override public String toString() {
return "Predicates.isNull()";
}
},
/** @see Predicates#notNull() */
NOT_NULL {
@Override public boolean apply(@Nullable Object o) {
return o != null;
}
@Override public String toString() {
return "Predicates.notNull()";
}
};
@SuppressWarnings("unchecked") // safe contravariant cast
<T> Predicate<T> withNarrowedType() {
return (Predicate<T>) this;
}
}
/** @see Predicates#not(Predicate) */
private static class NotPredicate<T> implements Predicate<T>, Serializable {
final Predicate<T> predicate;
NotPredicate(Predicate<T> predicate) {
this.predicate = checkNotNull(predicate);
}
@Override
public boolean apply(@Nullable T t) {
return !predicate.apply(t);
}
@Override public int hashCode() {
return ~predicate.hashCode();
}
@Override public boolean equals(@Nullable Object obj) {
if (obj instanceof NotPredicate) {
NotPredicate<?> that = (NotPredicate<?>) obj;
return predicate.equals(that.predicate);
}
return false;
}
@Override public String toString() {
return "Predicates.not(" + predicate.toString() + ")";
}
private static final long serialVersionUID = 0;
}
private static final Joiner COMMA_JOINER = Joiner.on(',');
/** @see Predicates#and(Iterable) */
private static class AndPredicate<T> implements Predicate<T>, Serializable {
private final List<? extends Predicate<? super T>> components;
private AndPredicate(List<? extends Predicate<? super T>> components) {
this.components = components;
}
@Override
public boolean apply(@Nullable T t) {
// Avoid using the Iterator to avoid generating garbage (issue 820).
for (int i = 0; i < components.size(); i++) {
if (!components.get(i).apply(t)) {
return false;
}
}
return true;
}
@Override public int hashCode() {
// add a random number to avoid collisions with OrPredicate
return components.hashCode() + 0x12472c2c;
}
@Override public boolean equals(@Nullable Object obj) {
if (obj instanceof AndPredicate) {
AndPredicate<?> that = (AndPredicate<?>) obj;
return components.equals(that.components);
}
return false;
}
@Override public String toString() {
return "Predicates.and(" + COMMA_JOINER.join(components) + ")";
}
private static final long serialVersionUID = 0;
}
/** @see Predicates#or(Iterable) */
private static class OrPredicate<T> implements Predicate<T>, Serializable {
private final List<? extends Predicate<? super T>> components;
private OrPredicate(List<? extends Predicate<? super T>> components) {
this.components = components;
}
@Override
public boolean apply(@Nullable T t) {
// Avoid using the Iterator to avoid generating garbage (issue 820).
for (int i = 0; i < components.size(); i++) {
if (components.get(i).apply(t)) {
return true;
}
}
return false;
}
@Override public int hashCode() {
// add a random number to avoid collisions with AndPredicate
return components.hashCode() + 0x053c91cf;
}
@Override public boolean equals(@Nullable Object obj) {
if (obj instanceof OrPredicate) {
OrPredicate<?> that = (OrPredicate<?>) obj;
return components.equals(that.components);
}
return false;
}
@Override public String toString() {
return "Predicates.or(" + COMMA_JOINER.join(components) + ")";
}
private static final long serialVersionUID = 0;
}
/** @see Predicates#equalTo(Object) */
private static class IsEqualToPredicate<T>
implements Predicate<T>, Serializable {
private final T target;
private IsEqualToPredicate(T target) {
this.target = target;
}
@Override
public boolean apply(T t) {
return target.equals(t);
}
@Override public int hashCode() {
return target.hashCode();
}
@Override public boolean equals(@Nullable Object obj) {
if (obj instanceof IsEqualToPredicate) {
IsEqualToPredicate<?> that = (IsEqualToPredicate<?>) obj;
return target.equals(that.target);
}
return false;
}
@Override public String toString() {
return "Predicates.equalTo(" + target + ")";
}
private static final long serialVersionUID = 0;
}
/** @see Predicates#instanceOf(Class) */
@GwtIncompatible("Class.isInstance")
private static class InstanceOfPredicate
implements Predicate<Object>, Serializable {
private final Class<?> clazz;
private InstanceOfPredicate(Class<?> clazz) {
this.clazz = checkNotNull(clazz);
}
@Override
public boolean apply(@Nullable Object o) {
return clazz.isInstance(o);
}
@Override public int hashCode() {
return clazz.hashCode();
}
@Override public boolean equals(@Nullable Object obj) {
if (obj instanceof InstanceOfPredicate) {
InstanceOfPredicate that = (InstanceOfPredicate) obj;
return clazz == that.clazz;
}
return false;
}
@Override public String toString() {
return "Predicates.instanceOf(" + clazz.getName() + ")";
}
private static final long serialVersionUID = 0;
}
/** @see Predicates#assignableFrom(Class) */
@GwtIncompatible("Class.isAssignableFrom")
private static class AssignableFromPredicate
implements Predicate<Class<?>>, Serializable {
private final Class<?> clazz;
private AssignableFromPredicate(Class<?> clazz) {
this.clazz = checkNotNull(clazz);
}
@Override
public boolean apply(Class<?> input) {
return clazz.isAssignableFrom(input);
}
@Override public int hashCode() {
return clazz.hashCode();
}
@Override public boolean equals(@Nullable Object obj) {
if (obj instanceof AssignableFromPredicate) {
AssignableFromPredicate that = (AssignableFromPredicate) obj;
return clazz == that.clazz;
}
return false;
}
@Override public String toString() {
return "Predicates.assignableFrom(" + clazz.getName() + ")";
}
private static final long serialVersionUID = 0;
}
/** @see Predicates#in(Collection) */
private static class InPredicate<T> implements Predicate<T>, Serializable {
private final Collection<?> target;
private InPredicate(Collection<?> target) {
this.target = checkNotNull(target);
}
@Override
public boolean apply(@Nullable T t) {
try {
return target.contains(t);
} catch (NullPointerException e) {
return false;
} catch (ClassCastException e) {
return false;
}
}
@Override public boolean equals(@Nullable Object obj) {
if (obj instanceof InPredicate) {
InPredicate<?> that = (InPredicate<?>) obj;
return target.equals(that.target);
}
return false;
}
@Override public int hashCode() {
return target.hashCode();
}
@Override public String toString() {
return "Predicates.in(" + target + ")";
}
private static final long serialVersionUID = 0;
}
/** @see Predicates#compose(Predicate, Function) */
private static class CompositionPredicate<A, B>
implements Predicate<A>, Serializable {
final Predicate<B> p;
final Function<A, ? extends B> f;
private CompositionPredicate(Predicate<B> p, Function<A, ? extends B> f) {
this.p = checkNotNull(p);
this.f = checkNotNull(f);
}
@Override
public boolean apply(@Nullable A a) {
return p.apply(f.apply(a));
}
@Override public boolean equals(@Nullable Object obj) {
if (obj instanceof CompositionPredicate) {
CompositionPredicate<?, ?> that = (CompositionPredicate<?, ?>) obj;
return f.equals(that.f) && p.equals(that.p);
}
return false;
}
@Override public int hashCode() {
return f.hashCode() ^ p.hashCode();
}
@Override public String toString() {
return p.toString() + "(" + f.toString() + ")";
}
private static final long serialVersionUID = 0;
}
/** @see Predicates#contains(Pattern) */
@GwtIncompatible("Only used by other GWT-incompatible code.")
private static class ContainsPatternPredicate
implements Predicate<CharSequence>, Serializable {
final Pattern pattern;
ContainsPatternPredicate(Pattern pattern) {
this.pattern = checkNotNull(pattern);
}
@Override
public boolean apply(CharSequence t) {
return pattern.matcher(t).find();
}
@Override public int hashCode() {
// Pattern uses Object.hashCode, so we have to reach
// inside to build a hashCode consistent with equals.
return Objects.hashCode(pattern.pattern(), pattern.flags());
}
@Override public boolean equals(@Nullable Object obj) {
if (obj instanceof ContainsPatternPredicate) {
ContainsPatternPredicate that = (ContainsPatternPredicate) obj;
// Pattern uses Object (identity) equality, so we have to reach
// inside to compare individual fields.
return Objects.equal(pattern.pattern(), that.pattern.pattern())
&& Objects.equal(pattern.flags(), that.pattern.flags());
}
return false;
}
@Override public String toString() {
String patternString = Objects.toStringHelper(pattern)
.add("pattern", pattern.pattern())
.add("pattern.flags", pattern.flags())
.toString();
return "Predicates.contains(" + patternString + ")";
}
private static final long serialVersionUID = 0;
}
/** @see Predicates#containsPattern(String) */
@GwtIncompatible("Only used by other GWT-incompatible code.")
private static class ContainsPatternFromStringPredicate
extends ContainsPatternPredicate {
ContainsPatternFromStringPredicate(String string) {
super(Pattern.compile(string));
}
@Override public String toString() {
return "Predicates.containsPattern(" + pattern.pattern() + ")";
}
private static final long serialVersionUID = 0;
}
private static <T> List<Predicate<? super T>> asList(
Predicate<? super T> first, Predicate<? super T> second) {
// TODO(kevinb): understand why we still get a warning despite @SafeVarargs!
return Arrays.<Predicate<? super T>>asList(first, second);
}
private static <T> List<T> defensiveCopy(T... array) {
return defensiveCopy(Arrays.asList(array));
}
static <T> List<T> defensiveCopy(Iterable<T> iterable) {
ArrayList<T> list = new ArrayList<T>();
for (T element : iterable) {
list.add(checkNotNull(element));
}
return list;
}
}