Convert Runnable to Supplier

Question

How can a Runnable be converted to a Supplier?

public <T> T useSupplier(Supplier<T> supplier) {
    // Does something with supplier and returns supplied value
    ...
    return value;
}

public void useRunnable(Runnable runnable) {
    // Somehow convert runnable to Supplier
    ...
    useSupplier(supplier);
}

Here I would like to reuse the method useSupplier for useRunnable, for example because I do not want to duplicate the code. The behavior of useSupplier does not matter for this question, let's say it wraps thrown exceptions, or uses the supplier in a synchronized block.

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Edit: To clarify, the method useSupplier does not interact with the supplied value, it just returns it. The functionality of useSupplier is to retrieve the value from the supplier in some context, in my case it catches (specific) RuntimeExceptions, creates a new exception with it as cause and throws it:

public <T> T useSupplier(Supplier<T> supplier) {
    try {
        return supplier.get();
    }
    catch (RuntimeException runtimeException) {
        throw new MyException("Supplier threw exception", runtimeException);
    }
}

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The following solutions do not work (in Java 8):

useSupplier(runnable);
useSupplier(runnable::run);
useSupplier((Supplier<Void>) runnable::run);

One solution I could come up with is creating a new Supplier which returns an arbitrary value:

useSupplier(() -> {
    runnable.run();
    return null;
});

Is there a smaller solution?

Edit: As pointed out by Holger in the comments, using runnable::run will also create new lambda instances since it is stateful, see also this answer.

Answer 1

In your case you cannot avoid creating new object. Even if there is a method somewhere that converts a Runnable to a Supplier, it will create an object there. So your solution is valid, you won't find any better.

Pay attention to that Supplier is expected to provide values and Runnable just represents an action. They are used for different purposes. So your need of converting Runnable to Supplier may be a result of a design problem involved.