https://github.com/ReactiveX/RxJava: Reactive Extensions for Java
  • David Karnok 
Copyright (c) 2016-present, RxJava Contributors.
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.

/**
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * 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 io.reactivex.exceptions;

import io.reactivex.annotations.*;
import io.reactivex.internal.util.ExceptionHelper;


Utility class to help propagate checked exceptions and rethrow exceptions
designated as fatal.

/**
 * Utility class to help propagate checked exceptions and rethrow exceptions
 * designated as fatal.
 */
public final class Exceptions {

    
Utility class. 
/** Utility class. */
    private Exceptions() {
        throw new IllegalStateException("No instances!");
    }
    
Convenience method to throw a RuntimeException and Error directly or wrap any other exception type into a RuntimeException. 
Params:
  • t – the exception to throw directly or wrapped
Returns:because propagate itself throws an exception or error, this is a sort of phantom return value; propagate does not actually return anything
/**
     * Convenience method to throw a {@code RuntimeException} and {@code Error} directly
     * or wrap any other exception type into a {@code RuntimeException}.
     * @param t the exception to throw directly or wrapped
     * @return because {@code propagate} itself throws an exception or error, this is a sort of phantom return
     *         value; {@code propagate} does not actually return anything
     */
    @NonNull
    public static RuntimeException propagate(@NonNull Throwable t) {
        /*
         * The return type of RuntimeException is a trick for code to be like this:
         *
         * throw Exceptions.propagate(e);
         *
         * Even though nothing will return and throw via that 'throw', it allows the code to look like it
         * so it's easy to read and understand that it will always result in a throw.
         */
        throw ExceptionHelper.wrapOrThrow(t);
    }

    
Throws a particular Throwable only if it belongs to a set of "fatal" error varieties. These varieties are as follows: 
    

  • VirtualMachineError
    • 

  • ThreadDeath
    • 

  • LinkageError
    • 

 This can be useful if you are writing an operator that calls user-supplied code, and you want to notify subscribers of errors encountered in that code by calling their onError methods, but only if the errors are not so catastrophic that such a call would be futile, in which case you simply want to rethrow the error. 
Params:
  • t –  the Throwable to test and perhaps throw
See Also:
/**
     * Throws a particular {@code Throwable} only if it belongs to a set of "fatal" error varieties. These
     * varieties are as follows:
     * <ul>
     * <li>{@code VirtualMachineError}</li>
     * <li>{@code ThreadDeath}</li>
     * <li>{@code LinkageError}</li>
     * </ul>
     * This can be useful if you are writing an operator that calls user-supplied code, and you want to
     * notify subscribers of errors encountered in that code by calling their {@code onError} methods, but only
     * if the errors are not so catastrophic that such a call would be futile, in which case you simply want to
     * rethrow the error.
     *
     * @param t
     *         the {@code Throwable} to test and perhaps throw
     * @see <a href="https://github.com/ReactiveX/RxJava/issues/748#issuecomment-32471495">RxJava: StackOverflowError is swallowed (Issue #748)</a>
     */
    public static void throwIfFatal(@NonNull Throwable t) {
        // values here derived from https://github.com/ReactiveX/RxJava/issues/748#issuecomment-32471495
        if (t instanceof VirtualMachineError) {
            throw (VirtualMachineError) t;
        } else if (t instanceof ThreadDeath) {
            throw (ThreadDeath) t;
        } else if (t instanceof LinkageError) {
            throw (LinkageError) t;
        }
    }
}