深入解析java中的locale

在项目中经常要用到将字符串解析成Locale，但是没有一个比较好用的类。
java本身提供了3个构造函数，但是实际使用过程中，需要自己解析，比较繁琐。
Locale(langugae)
locale(language,country)

Locale(String language, String country, String variant)
Apache 有个 LocaleUtils.toLocale(String language)但是不支持最后2个字符为小写的，如:zh_CN支持， zh_cn就不支持。

参考其它方法，写了下面的类，做个笔记，也希望对解决类似问题的人有点帮助。

import java.util.Locale;
public class LocaleUtil
{
    private final static Locale DEFAULT_LOCALE = Locale.ENGLISH;

    public final static String IETF_SEPARATOR = "-"; 

    public final static String SEPARATOR = "_"; 

    public final static String EMPTY_STRING = "";

   
    public static Locale toLocale( String language )
    {
        if( !StringUtil.isNullOrEmpty( language ) )
        {
            return langToLocale( language, SEPARATOR );
        }
        return DEFAULT_LOCALE;
    }

     public static Locale langToLocale( String lang , String separator )
     {
           if( StringUtil.isNullOrEmpty( lang ) )
           {
                return DEFAULT_LOCALE;
           }
            String language = EMPTY_STRING;
            String country =  EMPTY_STRING;
            String variant =  EMPTY_STRING;
            int i1 = lang.indexOf( separator );
            if ( i1 < 0 )
            {
                language = lang;
            } else
            {
                language = lang.substring(0, i1);
                ++i1;
                int i2 = lang.indexOf( separator, i1);
                if (i2 < 0)
                {
                    country = lang.substring(i1);
                } else
                {
                    country = lang.substring(i1, i2);
                    variant = lang.substring(i2+1);
                }
            }

            if(language.length() == 2)
            {
               language = language.toLowerCase();
            }else
            {
              language = EMPTY_STRING;
            }

            if(country.length() == 2)
            {
               country = country.toUpperCase();
            }else
            {
              country = EMPTY_STRING;
            }

            if( (variant.length() > 0) &&
                ((language.length() == 2) ||(country.length() == 2)) )
            {
               variant = variant.toUpperCase();
            }else
            {
                variant = EMPTY_STRING;
            }

            return new Locale(language, country, variant );
        }
}

注意：

 public class StringUtil
{
    public static boolean isNullOrEmpty(String target) {
        return target == null || "".equals(target);
    }
}