Question

I am converting the following C# code to Java. Is there a Java equivalent to the .NET concept of Invariant Culture?

string upper = myString.ToUpperInvariant();

Since the Invariant Culture is really just the US culture, I could just do something like this in Java, but I’m wondering if there is a better way:

String upper = myString.toUpperCase(Locale.US);

Answer 1

Update: Java 6 introduced Locale.ROOT which is described as:

This is regarded as the base locale of all locales, and is used as the language/country neutral locale for the locale sensitive operations.

This is probably better than using US, but I haven’t checked it against the code below.

---

No, that’s basically the right way to go. While there are differences between the US culture and the invariant culture in terms of formatting, I don’t believe they affect casing rules.

EDIT: Actually, a quick test program shows there are characters which are upper-cased differently in .NET in the US culture to in the invariant culture:

using System;
using System.Globalization;

class Test
{
    static void Main()
    {
        CultureInfo us = new CultureInfo("en-US");
        for (int i = 0; i < 65536; i++)
        {
            char c = (char) i;
            string s = c.ToString();
            if (s.ToUpperInvariant() != s.ToUpper(us))
            {
                Console.WriteLine(i.ToString("x4"));
            }
        }
    }    
}

Output:

00b5
0131
017f
01c5
01c8
01cb
01f2
0345
0390
03b0
03c2
03d0
03d1
03d5
03d6
03f0
03f1
03f5
1e9b
1fbe

I don’t have time to look at these right now, but it’s worth investigating. I don’t know if the same differences would apply in Java – you probably want to take a sample of them and work out what you want your code to do.

EDIT: And just to be completist, it’s worth mentioning that that only checks for individual characters… whereas you’re really upper-casing whole strings, which can make a difference.

Looking at the Java code for upper-casing, that appears to only have locale-specific behaviour for tr, az and lt countries. I know that tr is Turkey, but I don’t know about the others…