Returning an empty array

Both foo() and bar() may generate warnings in some IDEs. For example, IntelliJ IDEA will generate a Allocation of zero-length array warning.

An alternative approach is to use Apache Commons Lang 3 ArrayUtils.toArray() function with empty arguments:

public File[] bazz() {
    return ArrayUtils.toArray();
}

This approach is both performance and IDE friendly, yet requires a 3rd party dependency. However, if you already have commons-lang3 in your classpath, you could even use statically-defined empty arrays for primitive types:

public String[] bazz() {
    return ArrayUtils.EMPTY_STRING_ARRAY;
}

A different way to return an empty array is to use a constant as all empty arrays of a given type are the same.

private static final File[] NO_FILES = {};
private static File[] bar(){
    return NO_FILES;
}

Definitely the second one. In the first one, you use a constant empty List<?> and then convert it to a File[], which requires to create an empty File[0] array. And that is what you do in the second one in one single step.