/**
* Copyright 2014 Netflix, Inc.
*
* 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 rx.internal.util;
import rx.functions.
Func1;
/**
* Utility functions for internal use that we don't want part of the public API.
*/
public final class
UtilityFunctions {
/** Utility class. */
private
UtilityFunctions() {
throw new
IllegalStateException("No instances!");
}
/**
* Returns a function that always returns {@code true}.
*
* @param <T> the value type
* @return a {@link Func1} that accepts an Object and returns the Boolean {@code true}
*/
public static <T>
Func1<? super T,
Boolean>
alwaysTrue() {
return
AlwaysTrue.
INSTANCE;
}
/**
* Returns a function that always returns {@code false}.
*
* @param <T> the value type
* @return a {@link Func1} that accepts an Object and returns the Boolean {@code false}
*/
public static <T>
Func1<? super T,
Boolean>
alwaysFalse() {
return
AlwaysFalse.
INSTANCE;
}
/**
* Returns a function that always returns the Object it is passed.
*
* @param <T> the input and output value type
* @return a {@link Func1} that accepts an Object and returns the same Object
*/
@
SuppressWarnings("unchecked")
public static <T>
Func1<T, T>
identity() {
return (
Func1<T, T>)
Identity.
INSTANCE;
}
enum
AlwaysTrue implements
Func1<
Object,
Boolean> {
INSTANCE;
@
Override
public
Boolean call(
Object o) {
return true;
}
}
enum
AlwaysFalse implements
Func1<
Object,
Boolean> {
INSTANCE;
@
Override
public
Boolean call(
Object o) {
return false;
}
}
enum
Identity implements
Func1<
Object,
Object> {
INSTANCE;
@
Override
public
Object call(
Object o) {
return
o;
}
}
}