Kata

1. nope it's not in java (edit: I talked about the sample tests)

import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class ExampleTest {
    @Test
    public void exampleTests() {
        assertEquals("かた", Kata.romajiToHiragana("kata")); // form (of practice)
        assertEquals("いえ", Kata.romajiToHiragana("ie")); // house
        assertEquals("おまつり", Kata.romajiToHiragana("omatsuri")); // festival
        assertEquals("ちはやふる", Kata.romajiToHiragana("chihayafuru")); // a popular manga
        assertEquals("さっか", Kata.romajiToHiragana("sakka")); // writer
        assertEquals("がんばって", Kata.romajiToHiragana("ganbatte")); // good luck
        assertEquals("びょういん", Kata.romajiToHiragana("byouin")); // hispital
        assertEquals("こんにちは", Kata.romajiToHiragana("konnichiha")); // hello
    }
}

2. seems you don't understand the reason behind my suggestions. Note that I didn't raise an issue, just a suggestion. Meaning all is working, but the description, for occidental people is somewhat suboptimal. Why not make some small changes to it so that it's easier for "us" to find our way in it? I realized after I posted my previous message that the n/ん was effectively in the first table. Where he actually has nothing to do since it's the only entry there that is not consistent with the principle of the table itself (it's in the first line, but does not care about having a a after it. That doesn't make sense)

3. look at my solution, you'll see that those three keys aren't necessary.

Final note: Are you really down voting the guy who's trying to improvre your kata...? That'd be a nice joke...

Shouldn't apostrophe be used in cases like "んゆ" => "n'yu"?

It is one of the possible solutions, though far from widely used.

Of course there are still other problems with this scheme, specifically with distinguishing long vowels from two short vowels (which macrons are supposed to solve, like yōkai, but it's not widely used either). And we haven't even handled the supposed now deprecated kanas yet, which does pop up from time to time. Romaji is never really a fully adequate system.

Added the concatenated syllables table to the map instead of just changing the description. It's probably the best design choice.