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Small extensions for the core Java language libraries.
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/*
 * Copyright 2016 Yetamine
 *
 * 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 net.yetamine.lang.exceptions;

import java.util.Objects;

/**
 * Thrown when a checked exception shall be passed through as a boundary that
 * does not allow such checked exception, but the checked exception is desired
 * on a upper level. For instance, a callback code throws copes with a checked
 * exception which should be passed, but the calling code does not allow to,
 * although it relays unchecked exceptions from the callback to the caller.
 *
 * 
 * The common practice is wrapping the checked exception in an unchecked one.
 * This exception serves exactly to this one purpose and works especially well
 * when coupled with {@link Throwing} for unwrapping the cause and rethrowing.
 *
 * 
 * The name of this exception, "unchecked", has actually two meanings. First: it
 * is an unchecked exception and therefore allows to convey a checked exception,
 * as described above; second: it carries an exception which impacts might not
 * be checked thoroughly and therefore probably requires further handling. The
 * latter meaning suggests that it is better to catch such an exception early,
 * handle its root cause properly, e.g., by throwing another, more appropriate
 * exception. Note that {@link InterruptedException} needs special attention,
 * using the dedicated {@link InterruptionException} for handling it should be
 * preferred.
 */
public class UncheckedException extends RuntimeException {

    /** Serialization version: 1 */
    private static final long serialVersionUID = 1L;

    /**
     * Create a new instance with the specified cause and a detail message
     * constructed from the cause (if not {@code null}).
     *
     * @param cause
     *            the cause. It must not be {@code null}.
     */
    public UncheckedException(Throwable cause) {
        super(Objects.requireNonNull(cause));
    }

    /**
     * Returns the root cause of the exception which is not an
     * {@link UncheckedException} instance.
     *
     * @return the root cause
     */
    public final Throwable getRoot() {
        Throwable result = getCause();
        while (result instanceof UncheckedException) {
            result = result.getCause();
        }

        assert (result != null);
        return result;
    }

    /**
     * Throws a new {@link UncheckedException} that carries the given exception
     * as the cause.
     *
     * @param t
     *            the exception to wrap. It must not be {@code null}.
     */
    public static void raise(Throwable t) {
        throw new UncheckedException(t);
    }

    /**
     * Throws a new {@link UncheckedException} that carries the given exception
     * as the cause if the exception is not an {@link Error}, which is rethrown
     * without wrapping.
     *
     * @param t
     *            the exception to wrap. It must not be {@code null}.
     */
    public static void enclose(Throwable t) {
        if (t instanceof Error) {
            throw (Error) t;
        }

        raise(t);
    }

    /**
     * Throws a new {@link UncheckedException} that carries the given exception
     * as the cause if the exception is a checked exception; any {@link Error}
     * and {@link RuntimeException} are rethrown without wrapping.
     *
     * @param t
     *            the exception to wrap. It must not be {@code null}.
     */
    public static void rethrow(Throwable t) {
        if (t instanceof RuntimeException) {
            throw (RuntimeException) t;
        }

        if (t instanceof Error) {
            throw (Error) t;
        }

        raise(t);
    }
}