commons-lang/src/main/java/org/apache/commons/lang3/Functions.java

/*
 * 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.Method;
import java.lang.reflect.UndeclaredThrowableException;
import java.util.ArrayList;

import org.apache.commons.lang3.exception.ExceptionUtils;

/** 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
 * <pre>
 *   Consumer<java.lang.reflect.Method> consumer = (m) -> {
 *       try {
 *           m.invoke(o, args);
 *       } catch (Throwable t) {
 *           throw Functions.rethrow(t);
 *       }
 *   };
 * </pre>
 * By replacing a {@link Consumer Consumer<O>} with a
 * {@link FailableConsumer FailableConsumer<O,? extends Throwable}, this can be
 * written like follows:
 * <pre>
 *   Functions.accept((m) -> m.invoke(o,args));
 * </pre>
 * 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<T extends Throwable> {
		public void run() throws T;
	}
	@FunctionalInterface
	public interface FailableCallable<O,T extends Throwable> {
		public O call() throws T;
	}
	@FunctionalInterface
	public interface FailableConsumer<O,T extends Throwable> {
		public void accept(O pObject) throws T;
	}
	@FunctionalInterface
	public interface FailableBiConsumer<O1,O2,T extends Throwable> {
		public void accept(O1 pObject1, O2 pObject2) throws T;
	}
	@FunctionalInterface
	public interface FailableFunction<I,O,T extends Throwable> {
		public O apply(I pInput) throws T;
	}
	@FunctionalInterface
	public interface FailableBiFunction<I1,I2,O,T extends Throwable> {
		public O apply(I1 pInput1, I2 pInput2) throws T;
	}

	public static <T extends Throwable> void run(FailableRunnable<T> pRunnable) {
		try {
			pRunnable.run();
		} catch (Throwable t) {
			throw rethrow(t);
		}
	}

	public static <O,T extends Throwable> O call(FailableCallable<O,T> pCallable) {
		try {
			return pCallable.call();
		} catch (Throwable t) {
			throw rethrow(t);
		}
	}

	public static <O,T extends Throwable> void accept(FailableConsumer<O,T> pConsumer, O pObject) {
		try {
			pConsumer.accept(pObject);
		} catch (Throwable t) {
			throw rethrow(t);
		}
	}

	public static <O1,O2,T extends Throwable> void accept(FailableBiConsumer<O1,O2,T> pConsumer, O1 pObject1, O2 pObject2) {
		try {
			pConsumer.accept(pObject1, pObject2);
		} catch (Throwable t) {
			throw rethrow(t);
		}
	}

	public static <I,O,T extends Throwable> O apply(FailableFunction<I,O,T> pFunction, I pInput) {
		try {
			return pFunction.apply(pInput);
		} catch (Throwable t) {
			throw rethrow(t);
		}
	}

	public static <I1,I2,O,T extends Throwable> O apply(FailableBiFunction<I1,I2,O,T> pFunction, I1 pInput1, I2 pInput2) {
		try {
			return pFunction.apply(pInput1, pInput2);
		} catch (Throwable t) {
			throw rethrow(t);
		}
	}

	public static RuntimeException rethrow(Throwable pThrowable) {
		if (pThrowable == null) {
			throw new NullPointerException("The Throwable must not be null.");
		} else {
			if (pThrowable instanceof RuntimeException) {
				throw (RuntimeException) pThrowable;
			} else if (pThrowable instanceof Error) {
				throw (Error) pThrowable;
			} else if (pThrowable instanceof IOException) {
				throw new UncheckedIOException((IOException) pThrowable);
			} else {
				throw new UndeclaredThrowableException(pThrowable);
			}
		}
	}

	public static void test() throws Exception {
		run(() -> ArrayList.class.newInstance());
	}
}