Difference between File.separator and slash in pat

Question

What is the difference between using File.separator and a normal / in a Java Path-String?

In contrast to double backslash \\ platform independence seems not to be the reason, since both versions work under Windows and Unix.

public class SlashTest {
    @Test
    public void slash() throws Exception {
        File file = new File("src/trials/SlashTest.java");
        assertThat(file.exists(), is(true));
    }

    @Test
    public void separator() throws Exception {
        File file = new File("src" + File.separator + "trials" + File.separator + "SlashTest.java");
        assertThat(file.exists(), is(true));
    }
}

To rephrase the question, if / works on Unix and Windows, why should one ever want to use File.separator?

Answer 1

portability plain and simple.

Answer 2

"Java SE8 for Programmers" claims that the Java will cope with either. (pp. 480, last paragraph). The example claims that:

c:\Program Files\Java\jdk1.6.0_11\demo/jfc

will parse just fine. Take note of the last (Unix-style) separator.

It's tacky, and probably error-prone, but it is what they (Deitel and Deitel) claim.

I think the confusion for people, rather than Java, is reason enough not to use this (mis?)feature.