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Kiwi is a utility library. We really like Google's Guava, and also use Apache Commons. But if they don't have something we need, and we think it is useful, this is where we put it.

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package org.kiwiproject.base;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Extension of {@link Runnable} that never lets exceptions escape. Useful for things like scheduled executions
 * using {@link java.util.concurrent.ScheduledExecutorService} where an intermittent error should not cause the
 * executor to suppress future executions (which is the default behavior).
 */
@FunctionalInterface
public interface CatchingRunnable extends Runnable {

    /**
     * Wraps {@link #runSafely()} in a try/catch. Logs exceptions and will call {@link #handleExceptionSafely(Exception)}
     * to permit handling of any thrown exceptions.
     */
    @Override
    default void run() {
        try {
            runSafely();
        } catch (Exception e) {
            getLogger().error("Error occurred calling runSafely", e);

            try {
                handleExceptionSafely(e);
            } catch (Exception ex) {
                getLogger().error("Error occurred calling handleExceptionSafely", ex);
            }
        }
    }

    private static Logger getLogger() {
        return LoggerFactory.getLogger(CatchingRunnable.class);
    }

    /**
     * Handle an exception thrown by {@link #runSafely()}.
     *
     * @param exception the {@link Exception} to handle
     */
    default void handleExceptionSafely(Exception exception) {
        // no-op by default; override if desired
    }

    /**
     * The logic that could throw a {@link RuntimeException}.
     */
    void runSafely();
}