Is there a way in Java to convert an integer to its ordinal name?

Using the excellent ICU4J (there's also an excellent C version) you can also do this and get the Ordinals as plain words;

RuleBasedNumberFormat nf = new RuleBasedNumberFormat(Locale.UK, RuleBasedNumberFormat.SPELLOUT);
for(int i = 0; i <= 30; i++)
{
    System.out.println(i + " -> "+nf.format(i, "%spellout-ordinal"));
}

for example produces

0 -> zeroth
1 -> first
2 -> second
3 -> third
4 -> fourth
5 -> fifth
6 -> sixth
7 -> seventh
8 -> eighth
9 -> ninth
10 -> tenth
11 -> eleventh
12 -> twelfth
13 -> thirteenth
14 -> fourteenth
15 -> fifteenth
16 -> sixteenth
17 -> seventeenth
18 -> eighteenth
19 -> nineteenth
20 -> twentieth
21 -> twenty-first
22 -> twenty-second
23 -> twenty-third
24 -> twenty-fourth
25 -> twenty-fifth
26 -> twenty-sixth
27 -> twenty-seventh
28 -> twenty-eighth
29 -> twenty-ninth
30 -> thirtieth

If you're OK with 1st, 2nd, 3rd etc, here's some simple code that will correctly handle any integer:

public static String ordinal(int i) {
    String[] suffixes = new String[] { "th", "st", "nd", "rd", "th", "th", "th", "th", "th", "th" };
    switch (i % 100) {
    case 11:
    case 12:
    case 13:
        return i + "th";
    default:
        return i + suffixes[i % 10];

    }
}

Here's some tests for edge cases:

public static void main(String[] args) {
    int[] tests = {0, 1, 2, 3, 4, 5, 10, 11, 12, 13, 14, 20, 21, 22, 23, 24, 100, 101, 102, 103, 104, 111, 112, 113, 114, 1000};
    for (int test : tests) {
        System.out.println(ordinal(test));
    }
}

Output:

0th
1st
2nd
3rd
4th
5th
10th
11th
12th
13th
14th
20th
21st
22nd
23rd
24th
100th
101st
102nd
103rd
104th
111th
112th
113th
114th
1000th

Another solution

public static String ordinal(int i) {
    int mod100 = i % 100;
    int mod10 = i % 10;
    if(mod10 == 1 && mod100 != 11) {
        return i + "st";
    } else if(mod10 == 2 && mod100 != 12) {
        return i + "nd";
    } else if(mod10 == 3 && mod100 != 13) {
        return i + "rd";
    } else {
        return i + "th";
    }
}

Pro: does not require an array to be initialized (less garbage)
Con: not a one-liner...

I've figured out how to do this in Android in a pretty simple way. All you need to do is to add the dependency to your app's build.gradle file:

implementation "com.ibm.icu:icu4j:53.1"

Next, create this method:

Kotlin:

fun Number?.getOrdinal(): String? {
    if (this == null) {
        return null
    }

    val format = "{0,ordinal}"

    return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
        android.icu.text.MessageFormat.format(format, this)
    } else {
        com.ibm.icu.text.MessageFormat.format(format, this)
    }
}

Java:

public static String getNumberOrdinal(Number number) {
        if (number == null) {
            return null;
        }

        String format = "{0,ordinal}";

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            return android.icu.text.MessageFormat.format(format, number);
        } else {
            return com.ibm.icu.text.MessageFormat.format(format, number);
        }
    }

Then, you can simply use it like this:

Kotlin:

val ordinal = 2.getOrdinal()

Java:

String ordinal = getNumberOrdinal(2)

How it works

Starting from Android N (API 24) Android uses icu.text instead of regular java.text (more info here), which already contains internationalized implementation for ordinal numbers. So the solution is obviously simple - to add the icu4j library to the project and use it on versions below the Nougat