org.apache.commons.lang3.function.FailableFunction Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of commons-lang3 Show documentation

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. The code is tested using the latest revision of the JDK for supported LTS releases: 8, 11, 17 and 21 currently. See https://github.com/apache/commons-lang/blob/master/.github/workflows/maven.yml Please ensure your build environment is up-to-date and kindly report any build issues.

There is a newer version: 3.17.0

Show newest version

/*
 * 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.function;

import java.util.Objects;
import java.util.function.Function;

/**
 * A functional interface like {@link Function} that declares a {@link Throwable}.
 *
 * @param  Input type 1.
 * @param  Return type.
 * @param  The kind of thrown exception or error.
 * @since 3.11
 */
@FunctionalInterface
public interface FailableFunction {

    /** NOP singleton */
    @SuppressWarnings("rawtypes")
    FailableFunction NOP = t -> null;

    /**
     * Starts a fluent chain like {@code function(foo::bar).andThen(...).andThen(...).apply(...);}
     *
     * @param  Input type.
     * @param  Return type.
     * @param  The kind of thrown exception or error.
     * @param function   the argument to return.
     * @return the argument
     * @since 3.14.0
     */
    static  FailableFunction function(final FailableFunction function) {
        return function;
    }

    /**
     * Returns a function that always returns its input argument.
     *
     * @param  the type of the input and output objects to the function
     * @param  The kind of thrown exception or error.
     * @return a function that always returns its input argument
     */
    static  FailableFunction identity() {
        return t -> t;
    }

    /**
     * Returns The NOP singleton.
     *
     * @param  Consumed type.
     * @param  Return type.
     * @param  The kind of thrown exception or error.
     * @return The NOP singleton.
     */
    @SuppressWarnings("unchecked")
    static  FailableFunction nop() {
        return NOP;
    }

    /**
     * Returns a composed {@link FailableFunction} like {@link Function#andThen(Function)}.
     *
     * @param  the output type of the {@code after} function, and of the composed function.
     * @return a composed {@link FailableFunction} like {@link Function#andThen(Function)}.
     * @param after the operation to perform after this one.
     * @throws NullPointerException when {@code after} is null.
     */
    default  FailableFunction andThen(final FailableFunction after) {
        Objects.requireNonNull(after);
        return (final T t) -> after.apply(apply(t));
    }

    /**
     * Applies this function.
     *
     * @param input the input for the function
     * @return the result of the function
     * @throws E Thrown when the function fails.
     */
    R apply(T input) throws E;

    /**
     * Returns a composed {@link FailableFunction} like {@link Function#compose(Function)}.
     *
     * @param  the input type to the {@code before} function, and to the composed function.
     * @param before the operator to apply before this one.
     * @return a composed {@link FailableFunction} like {@link Function#compose(Function)}.
     * @throws NullPointerException if before is null.
     * @see #andThen(FailableFunction)
     */
    default  FailableFunction compose(final FailableFunction before) {
        Objects.requireNonNull(before);
        return (final V v) -> apply(before.apply(v));
    }
}