Question

One problem with using Guava’s Optional type as arguments of methods is that you can’t simply write

// method declaration
public void foo(Optional<String> arg);

// compiler error
foo(Optional.absent());

due to type inference failing but instead have to add the type explicitly:

// real method call
foo(Optional.<String> absent());

How can I avoid it?

Answer 1

Just when writing the question, I thought of having

public class GuavaConstants {
    @SuppressWarnings( { "raw" })
    public static final Optional ABSENT = Optional.absent();

    // similar for empty ImmutableList, etc.
}

and then the call can look like

@SuppressWarnings( { "unchecked" })
foo(GuavaConstants.ABSENT);

Is there a better approach?