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Java 8+ functional interfaces with checked exceptions support
There is a newer version: 1.6.1
/*
 * Copyright 2016 the original author or 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.pivovarit.function;

import com.pivovarit.function.exception.WrappedException;

import java.util.Optional;
import java.util.function.Supplier;

import static java.util.Objects.requireNonNull;

/**
 * Represents a function that accepts zero arguments and returns some value.
 * Function might throw a checked exception instance.
 *
 * @param  the type of the output to the function
 * @param  the type of the thrown checked exception
 * @author Grzegorz Piwowarek
 */
@FunctionalInterface
public interface ThrowingSupplier {
    T get() throws E;

    /**
     * @return this Consumer instance as a new Function instance
     */
    default ThrowingFunction asFunction() {
        return arg -> get();
    }

    static  Supplier unchecked(ThrowingSupplier supplier) {
        return requireNonNull(supplier).uncheck();
    }

    static  Supplier> lifted(ThrowingSupplier supplier) {
        return requireNonNull(supplier).lift();
    }

    /**
     * Returns a new Supplier instance which rethrows the checked exception using the Sneaky Throws pattern
     * @return Supplier instance that rethrows the checked exception using the Sneaky Throws pattern
     */
    static  Supplier sneaky(ThrowingSupplier supplier) {
        requireNonNull(supplier);
        return () -> {
            try {
                return supplier.get();
            } catch (final Exception ex) {
                return SneakyThrowUtil.sneakyThrow(ex);
            }
        };
    }

    /**
     * @return a new Supplier instance which wraps thrown checked exception instance into a RuntimeException
     */
    default Supplier uncheck() {
        return () -> {
            try {
                return get();
            } catch (final Exception e) {
                throw new WrappedException(e);
            }
        };
    }

    /**
     * @return a new Supplier that returns the result as an Optional instance. In case of a failure or null, empty Optional is
     * returned
     */
    default Supplier> lift() {
        return () -> {
            try {
                return Optional.ofNullable(get());
            } catch (final Exception e) {
                return Optional.empty();
            }
        };
    }
}