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Apache Commons Lang, a package of Java utility classes for the
classes that are in java.lang's hierarchy, or are considered to be so
standard as to justify existence in java.lang.
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.commons.lang3;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.lang.reflect.UndeclaredThrowableException;
import java.util.Collection;
import java.util.Objects;
import java.util.concurrent.Callable;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.BiPredicate;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
import java.util.stream.Stream;
import org.apache.commons.lang3.Streams.FailableStream;
/** This class provides utility functions, and classes for working with the
* {@code java.util.function} package, or more generally, with Java 8
* lambdas.
* More specifically, it attempts to address the fact that lambdas are supposed
* not to throw Exceptions, at least not checked Exceptions, aka instances of
* {@link Exception}. This enforces the use of constructs like
* {@code
* Consumer consumer = (m) -> {
* try {
* m.invoke(o, args);
* } catch (Throwable t) {
* throw Functions.rethrow(t);
* }
* };
* }
* By replacing a {@link java.util.function.Consumer Consumer<O>} with a
* {@link FailableConsumer FailableConsumer<O,? extends Throwable>}, this can be
* written like follows:
* {@code
* Functions.accept((m) -> m.invoke(o,args));
* }
* Obviously, the second version is much more concise and the spirit of
* Lambda expressions is met better than the second version.
*/
public class Functions {
@FunctionalInterface
public interface FailableRunnable {
/**
* Runs the function.
* @throws T if the function fails
*/
void run() throws T;
}
@FunctionalInterface
public interface FailableCallable {
/**
* Calls the callable.
* @return The value returned from the callable
* @throws T if the callable fails
*/
O call() throws T;
}
@FunctionalInterface
public interface FailableConsumer {
/**
* Accepts the consumer.
* @param object the parameter for the consumable to accept
* @throws T if the consumer fails
*/
void accept(O object) throws T;
}
@FunctionalInterface
public interface FailableBiConsumer {
/**
* Accepts the consumer.
* @param object1 the first parameter for the consumable to accept
* @param object2 the second parameter for the consumable to accept
* @throws T if the consumer fails
*/
void accept(O1 object1, O2 object2) throws T;
}
@FunctionalInterface
public interface FailableFunction {
/**
* Apply the function.
* @param input the input for the function
* @return the result of the function
* @throws T if the function fails
*/
O apply(I input) throws T;
}
@FunctionalInterface
public interface FailableBiFunction {
/**
* Apply the function.
* @param input1 the first input for the function
* @param input2 the second input for the function
* @return the result of the function
* @throws T if the function fails
*/
O apply(I1 input1, I2 input2) throws T;
}
@FunctionalInterface
public interface FailablePredicate {
/**
* Test the predicate.
* @param object the object to test the predicate on
* @return the predicate's evaluation
* @throws T if the predicate fails
*/
boolean test(O object) throws T;
}
@FunctionalInterface
public interface FailableBiPredicate {
/**
* Test the predicate.
* @param object1 the first object to test the predicate on
* @param object2 the second object to test the predicate on
* @return the predicate's evaluation
* @throws T if the predicate fails
*/
boolean test(O1 object1, O2 object2) throws T;
}
@FunctionalInterface
public interface FailableSupplier {
/**
* Supplies an object
* @return the suppliers result
* @throws T if the supplier fails
*/
O get() throws T;
}
/**
* Converts the given {@link FailableRunnable} into a standard {@link Runnable}.
*
* @param runnable a {@code FailableRunnable}
* @return a standard {@code Runnable}
*/
public static Runnable asRunnable(final FailableRunnable runnable) {
return () -> run(runnable);
}
/**
* Converts the given {@link FailableConsumer} into a standard {@link Consumer}.
*
* @param the type used by the consumers
* @param consumer a {@code FailableConsumer}
* @return a standard {@code Consumer}
*/
public static Consumer asConsumer(final FailableConsumer consumer) {
return input -> accept(consumer, input);
}
/**
* Converts the given {@link FailableCallable} into a standard {@link Callable}.
*
* @param the type used by the callables
* @param callable a {@code FailableCallable}
* @return a standard {@code Callable}
*/
public static Callable asCallable(final FailableCallable callable) {
return () -> call(callable);
}
/**
* Converts the given {@link FailableBiConsumer} into a standard {@link BiConsumer}.
*
* @param the type of the first argument of the consumers
* @param the type of the second argument of the consumers
* @param consumer a failable {@code BiConsumer}
* @return a standard {@code BiConsumer}
*/
public static BiConsumer asBiConsumer(final FailableBiConsumer consumer) {
return (input1, input2) -> accept(consumer, input1, input2);
}
/**
* Converts the given {@link FailableFunction} into a standard {@link Function}.
*
* @param the type of the input of the functions
* @param the type of the output of the functions
* @param function a {code FailableFunction}
* @return a standard {@code Function}
*/
public static Function asFunction(final FailableFunction function) {
return input -> apply(function, input);
}
/**
* Converts the given {@link FailableBiFunction} into a standard {@link BiFunction}.
*
* @param the type of the first argument of the input of the functions
* @param the type of the second argument of the input of the functions
* @param the type of the output of the functions
* @param function a {@code FailableBiFunction}
* @return a standard {@code BiFunction}
*/
public static BiFunction asBiFunction(final FailableBiFunction function) {
return (input1, input2) -> apply(function, input1, input2);
}
/**
* Converts the given {@link FailablePredicate} into a standard {@link Predicate}.
*
* @param the type used by the predicates
* @param predicate a {@code FailablePredicate}
* @return a standard {@code Predicate}
*/
public static Predicate asPredicate(final FailablePredicate predicate) {
return input -> test(predicate, input);
}
/**
* Converts the given {@link FailableBiPredicate} into a standard {@link BiPredicate}.
*
* @param the type of the first argument used by the predicates
* @param the type of the second argument used by the predicates
* @param predicate a {@code FailableBiPredicate}
* @return a standard {@code BiPredicate}
*/
public static BiPredicate asBiPredicate(final FailableBiPredicate predicate) {
return (input1, input2) -> test(predicate, input1, input2);
}
/**
* Converts the given {@link FailableSupplier} into a standard {@link Supplier}.
*
* @param the type supplied by the suppliers
* @param supplier a {@code FailableSupplier}
* @return a standard {@code Supplier}
*/
public static Supplier asSupplier(final FailableSupplier supplier) {
return () -> get(supplier);
}
/**
* Runs a runnable and rethrows any exception as a {@link RuntimeException}.
* @param runnable The runnable to run
* @param the type of checked exception the runnable may throw
*/
public static void run(final FailableRunnable runnable) {
try {
runnable.run();
} catch (final Throwable t) {
throw rethrow(t);
}
}
/**
* Calls a callable and rethrows any exception as a {@link RuntimeException}.
* @param callable the callable to call
* @param the return type of the callable
* @param the type of checked exception the callable may throw
* @return the value returned from the callable
*/
public static O call(final FailableCallable callable) {
return get(callable::call);
}
/**
* Consumes a consumer and rethrows any exception as a {@link RuntimeException}.
* @param consumer the consumer to consume
* @param object the object to consume by {@code consumer}
* @param the type the consumer accepts
* @param the type of checked exception the consumer may throw
*/
public static void accept(final FailableConsumer consumer, final O object) {
run(() -> consumer.accept(object));
}
/**
* Consumes a consumer and rethrows any exception as a {@link RuntimeException}.
* @param consumer the consumer to consume
* @param object1 the first object to consume by {@code consumer}
* @param object2 the second object to consume by {@code consumer}
* @param the type of the first argument the consumer accepts
* @param the type of the second argument the consumer accepts
* @param the type of checked exception the consumer may throw
*/
public static void accept(final FailableBiConsumer consumer, final O1 object1, final O2 object2) {
run(() -> consumer.accept(object1, object2));
}
/**
* Applies a function and rethrows any exception as a {@link RuntimeException}.
* @param function the function to apply
* @param input the input to apply {@code function} on
* @param the type of the argument the function accepts
* @param the return type of the function
* @param the type of checked exception the function may throw
* @return the value returned from the function
*/
public static O apply(final FailableFunction function, final I input) {
return get(() -> function.apply(input));
}
/**
* Applies a function and rethrows any exception as a {@link RuntimeException}.
* @param function the function to apply
* @param input1 the first input to apply {@code function} on
* @param input2 the second input to apply {@code function} on
* @param the type of the first argument the function accepts
* @param the type of the second argument the function accepts
* @param the return type of the function
* @param the type of checked exception the function may throw
* @return the value returned from the function
*/
public static O apply(final FailableBiFunction function, final I1 input1, final I2 input2) {
return get(() -> function.apply(input1, input2));
}
/**
* Tests a predicate and rethrows any exception as a {@link RuntimeException}.
* @param predicate the predicate to test
* @param object the input to test by {@code predicate}
* @param the type of argument the predicate tests
* @param the type of checked exception the predicate may throw
* @return the boolean value returned by the predicate
*/
public static boolean test(final FailablePredicate predicate, final O object) {
return get(() -> predicate.test(object));
}
/**
* Tests a predicate and rethrows any exception as a {@link RuntimeException}.
* @param predicate the predicate to test
* @param object1 the first input to test by {@code predicate}
* @param object2 the second input to test by {@code predicate}
* @param the type of the first argument the predicate tests
* @param the type of the second argument the predicate tests
* @param the type of checked exception the predicate may throw
* @return the boolean value returned by the predicate
*/
public static boolean test(final FailableBiPredicate predicate, final O1 object1, final O2 object2) {
return get(() -> predicate.test(object1, object2));
}
/**
* Invokes the supplier, and returns the result.
* @param supplier The supplier to invoke.
* @param The suppliers output type.
* @param The type of checked exception, which the supplier can throw.
* @return The object, which has been created by the supplier
*/
public static O get(final FailableSupplier supplier) {
try {
return supplier.get();
} catch (final Throwable t) {
throw rethrow(t);
}
}
/**
* Converts the given stream into a {@link FailableStream}. The
* {@link FailableStream} consists of the same elements, than the
* input stream. However, failable lambdas, like
* {@link FailablePredicate}, {@link FailableFunction}, and
* {@link FailableConsumer} may be applied, rather than
* {@link Predicate}, {@link Function}, {@link Consumer}, etc.
* @param stream The stream, which is being converted into a
* {@link FailableStream}.
* @param The streams element type.
* @return The created {@link FailableStream}.
*/
public static FailableStream stream(final Stream stream) {
return new FailableStream<>(stream);
}
/**
* Converts the given collection into a {@link FailableStream}.
* The {@link FailableStream} consists of the collections
* elements. Shortcut for
*
* Functions.stream(collection.stream());
*
* @param collection The collection, which is being converted into a
* {@link FailableStream}.
* @param The collections element type. (In turn, the result
* streams element type.)
* @return The created {@link FailableStream}.
*/
public static FailableStream stream(final Collection collection) {
return new FailableStream<>(collection.stream());
}
/**
* A simple try-with-resources implementation, that can be used, if your
* objects do not implement the {@link AutoCloseable} interface. The method
* executes the {@code action}. The method guarantees, that all
* the {@code resources} are being executed, in the given order, afterwards,
* and regardless of success, or failure. If either the original action, or
* any of the resource action fails, then the first failure (aka
* {@link Throwable} is rethrown. Example use:
* {@code
* final FileInputStream fis = new FileInputStream("my.file");
* Functions.tryWithResources(useInputStream(fis), null, () -> fis.close());
* }
* @param action The action to execute. This object will always
* be invoked.
* @param errorHandler An optional error handler, which will be invoked finally,
* if any error occurred. The error handler will receive the first
* error, aka {@link Throwable}.
* @param resources The resource actions to execute. All resource
* actions will be invoked, in the given order. A resource action is an
* instance of {@link FailableRunnable}, which will be executed.
* @see #tryWithResources(FailableRunnable, FailableRunnable...)
*/
@SafeVarargs
public static void tryWithResources(final FailableRunnable action,
final FailableConsumer errorHandler,
final FailableRunnable... resources) {
final FailableConsumer actualErrorHandler;
if (errorHandler == null) {
actualErrorHandler = Functions::rethrow;
} else {
actualErrorHandler = errorHandler;
}
if (resources != null) {
for (final FailableRunnable failableRunnable : resources) {
Objects.requireNonNull(failableRunnable, "runnable");
}
}
Throwable th = null;
try {
action.run();
} catch (final Throwable t) {
th = t;
}
if (resources != null) {
for (final FailableRunnable runnable : resources) {
try {
runnable.run();
} catch (final Throwable t) {
if (th == null) {
th = t;
}
}
}
}
if (th != null) {
try {
actualErrorHandler.accept(th);
} catch (final Throwable t) {
throw rethrow(t);
}
}
}
/**
* A simple try-with-resources implementation, that can be used, if your
* objects do not implement the {@link AutoCloseable} interface. The method
* executes the {@code action}. The method guarantees, that all
* the {@code resources} are being executed, in the given order, afterwards,
* and regardless of success, or failure. If either the original action, or
* any of the resource action fails, then the first failure (aka
* {@link Throwable} is rethrown. Example use:
* {@code
* final FileInputStream fis = new FileInputStream("my.file");
* Functions.tryWithResources(useInputStream(fis), () -> fis.close());
* }
* @param action The action to execute. This object will always
* be invoked.
* @param resources The resource actions to execute. All resource
* actions will be invoked, in the given order. A resource action is an
* instance of {@link FailableRunnable}, which will be executed.
* @see #tryWithResources(FailableRunnable, FailableConsumer, FailableRunnable...)
*/
@SafeVarargs
public static void tryWithResources(final FailableRunnable action,
final FailableRunnable... resources) {
tryWithResources(action, null, resources);
}
/**
* Rethrows a {@link Throwable} as an unchecked exception. If the argument is
* already unchecked, namely a {@code RuntimeException} or {@code Error} then
* the argument will be rethrown without modification. If the exception is
* {@code IOException} then it will be wrapped into a {@code UncheckedIOException}.
* In every other cases the exception will be wrapped into a {@code
* UndeclaredThrowableException}
*
* Note that there is a declared return type for this method, even though it
* never returns. The reason for that is to support the usual pattern:
*
*
* throw rethrow(myUncheckedException);
*
*
* instead of just calling the method. This pattern may help the Java compiler to
* recognize that at that point an exception will be thrown and the code flow
* analysis will not demand otherwise mandatory commands that could follow the
* method call, like a {@code return} statement from a value returning method.
*
* @param throwable The throwable to rethrow ossibly wrapped into an unchecked exception
* @return Never returns anything, this method never terminates normally.
*/
public static RuntimeException rethrow(final Throwable throwable) {
Objects.requireNonNull(throwable, "throwable");
if (throwable instanceof RuntimeException) {
throw (RuntimeException) throwable;
} else if (throwable instanceof Error) {
throw (Error) throwable;
} else if (throwable instanceof IOException) {
throw new UncheckedIOException((IOException) throwable);
} else {
throw new UndeclaredThrowableException(throwable);
}
}
}