public static String join(Iterable<?> iterable, String separator) {
        return join( iterable, separator, null );
    }
@Test
    public void testJoin() {
        assertThat( Strings.join( new ArrayList<String>(), "-" ) ).isEqualTo( "" );
        assertThat( Strings.join( Arrays.asList( "Hello", "World" ), "-" ) ).isEqualTo( "Hello-World" );
        assertThat( Strings.join( Arrays.asList( "Hello" ), "-" ) ).isEqualTo( "Hello" );
    }