将语言环境作为彼此子集进行比较的规范方法

Question

Assume I have a locale stored in some config in whatever format, that I can get a Locale object from. I then need to check that the current Locale is this locale or a subset of this locale .

So, what I'm looking for, in essence, is a method isSubsetLocale(Locale currentLocale, Locale configLocale) with these properties:

isSubsetLocale(Locale.forLanguageTag("en-US"), Locale.forLanguageTag("en")) == true;
isSubsetLocale(Locale.forLanguageTag("en-US"), Locale.forLanguageTag("en-US")) == true;
isSubsetLocale(Locale.forLanguageTag("de-CH"), Locale.forLanguageTag("en")) == false;

// or even
isSubsetLocale(Locale.forLanguageTag("en-US"), Locale.forLanguageTag("")) == true;

I understand that in 99% of the cases I can just check if the config locale is a prefix of the current locale, but I'm wondering if there's a more idiomatic way to do it.

Answer 1

This might work:

public static boolean isSubsetLocale(Locale locale1, Locale locale2) {
    String tag1 = locale1.toLanguageTag();
    String tag2 = locale2.toLanguageTag();
    if (tag1.equals("und"))
        tag1 = "";
    if (tag2.equals("und"))
        tag2 = "";
    return tag1.startsWith(tag2);
}

Test

System.out.println(isSubsetLocale(Locale.forLanguageTag("en-US"), Locale.forLanguageTag("en")));
System.out.println(isSubsetLocale(Locale.forLanguageTag("en-US"), Locale.forLanguageTag("en-US")));
System.out.println(isSubsetLocale(Locale.forLanguageTag("de-CH"), Locale.forLanguageTag("en")));

System.out.println(isSubsetLocale(Locale.forLanguageTag("en-US"), Locale.forLanguageTag("")));
System.out.println(isSubsetLocale(Locale.forLanguageTag("en"), Locale.forLanguageTag("en-US")));

Output

true
true
false
true
false

Answer 2

Do you need something more than locale.getLanguage() for the comparison? That will give you the prefix for comparison.

Locale.forLanguageTag("en-US").getLanguage().equals(Locale.forLanguageTag("en").getLanguage()) //true;