与世界上其他每天使用the US uses month-day-year formats的人一样，
我想以编程方式确定用户使用的是月-月还是月-日。
我可以通过以下方法做到这一点，但是我不确定是否有更简单的方法？
String localisedDateFormat = ((SimpleDateFormat) SimpleDateFormat.getDateInstance()).toPattern().toLowerCase();
boolean usFormat = localisedDateFormat.indexOf('d') > localisedDateFormat.indexOf('m');
我认为DateTimeFormatter不可能做到这一点，因为您无法获得基础pattern。
答案 0 :(得分：0)
TL; DR：调用此帮助程序方法，该方法返回YMD，DMY或MDY。
public static String getDateFieldOrder(Locale locale) {
SimpleDateFormat fmt = ((SimpleDateFormat) DateFormat.getDateInstance(DateFormat.SHORT, locale));
return fmt.toPattern().replaceAll("[^yMd]|(?<=(.))\\1", "").toUpperCase();
}
要获取现场订单，请索取DateFormat，然后分析用于构建订单的模式：
SimpleDateFormat fmt = ((SimpleDateFormat) DateFormat.getDateInstance(DateFormat.SHORT, locale));
String pattern = fmt.toPattern();
这将为您提供如下模式：
dd.MM.yy
M/d/yy
y-MM-dd
d. M. y
因此，删除非字母和重复字母：
pattern = pattern.replaceAll("\\P{L}", "").replaceAll("(.)\\1+", "$1");
要查看可能的结果，可以运行以下代码（Java 5 +）：
Map<String, Set<String>> map = new TreeMap<String, Set<String>>();
for (Locale locale : Locale.getAvailableLocales()) {
SimpleDateFormat fmt = ((SimpleDateFormat) DateFormat.getDateInstance(DateFormat.SHORT, locale));
String pattern = fmt.toPattern().replaceAll("\\P{L}", "").replaceAll("(.)\\1+", "$1");
Set<String> set = map.get(pattern);
if (set == null)
map.put(pattern, set = new TreeSet<String>());
set.add(locale.getDisplayName(Locale.US));
}
for (Entry<String, Set<String>> entry : map.entrySet())
System.out.println(entry.getKey() + " = " + entry.getValue());
示例输出（Java 11）
GyMd = [Japanese (Japan, JP, Japanese Calendar)]
Mdy = [Bodo, Bodo (India), Cherokee, Cherokee (United States), English, English (American Samoa), English (Burundi), English (Guam), English (Marshall Islands), English (Northern Mariana Islands), English (Puerto Rico), English (U.S. Outlying Islands), English (U.S. Virgin Islands), English (United States), English (United States, Computer), Ewe, Ewe (Ghana), Ewe (Togo), Filipino, Filipino (Philippines), Kashmiri, Kashmiri (India), Odia, Odia (India), Spanish (Panama), Spanish (Puerto Rico), Zulu, Zulu (South Africa)]
dMy = [Aghem, Aghem (Cameroon), Albanian, Albanian (Albania), Albanian (Kosovo), Albanian (Macedonia), Amharic, Amharic (Ethiopia), Arabic, Arabic (Algeria), Arabic (Bahrain), Arabic (Chad), Arabic (Comoros), Arabic (Djibouti), Arabic (Egypt), Arabic (Eritrea), Arabic (Iraq), Arabic (Israel), Arabic (Jordan), Arabic (Kuwait), Arabic (Lebanon), Arabic (Libya), Arabic (Mauritania), Arabic (Morocco), Arabic (Oman), Arabic (Palestinian Territories), Arabic (Qatar), Arabic (Saudi Arabia), Arabic (Somalia), Arabic (South Sudan), Arabic (Sudan), Arabic (Syria), Arabic (Tunisia), Arabic (United Arab Emirates), Arabic (Western Sahara), Arabic (World), Arabic (Yemen), Armenian, Armenian (Armenia), Assamese, Assamese (India), Asturian, Asturian (Spain), Asu, Asu (Tanzania), Azerbaijani, Azerbaijani (Cyrillic), Azerbaijani (Cyrillic, Azerbaijan), Azerbaijani (Latin), Azerbaijani (Latin, Azerbaijan), Bafia, Bafia (Cameroon), Bambara, Bambara (Mali), Bangla, Bangla (Bangladesh), Bangla (India), Basaa, Basaa (Cameroon), Belarusian, Belarusian (Belarus), Bemba, Bemba (Zambia), Bena, Bena (Tanzania), Bosnian, Bosnian (Cyrillic), Bosnian (Cyrillic, Bosnia & Herzegovina), Bosnian (Latin), Bosnian (Latin, Bosnia & Herzegovina), Breton, Breton (France), Burmese, Burmese (Myanmar (Burma)), Catalan, Catalan (Andorra), Catalan (France), Catalan (Italy), Catalan (Spain), Catalan (Spain, Valencian), Central Atlas Tamazight, Central Atlas Tamazight (Morocco), Chakma, Chakma (Bangladesh), Chakma (India), Chiga, Chiga (Uganda), Chinese (Hong Kong SAR China), Chinese (Simplified, Hong Kong SAR China), Chinese (Simplified, Macau SAR China), Chinese (Simplified, Singapore), Chinese (Singapore), Chinese (Traditional, Hong Kong SAR China), Chinese (Traditional, Macau SAR China), Colognian, Colognian (Germany), Croatian, Croatian (Bosnia & Herzegovina), Croatian (Croatia), Czech, Czech (Czechia), Danish, Danish (Denmark), Danish (Greenland), Duala, Duala (Cameroon), Dutch, Dutch (Aruba), Dutch (Belgium), Dutch (Caribbean Netherlands), Dutch (Curaçao), Dutch (Netherlands), Dutch (Sint Maarten), Dutch (Suriname), Embu, Embu (Kenya), English (Anguilla), English (Antigua & Barbuda), English (Australia), English (Austria), English (Bahamas), English (Barbados), English (Belgium), English (Belize), English (Bermuda), English (Botswana), English (British Indian Ocean Territory), English (British Virgin Islands), English (Cameroon), English (Cayman Islands), English (Christmas Island), English (Cocos (Keeling) Islands), English (Cook Islands), English (Cyprus), English (Denmark), English (Diego Garcia), English (Dominica), English (Eritrea), English (Europe), English (Falkland Islands), English (Fiji), English (Finland), English (Gambia), English (Germany), English (Ghana), English (Gibraltar), English (Grenada), English (Guernsey), English (Guyana), English (Hong Kong SAR China), English (India), English (Ireland), English (Isle of Man), English (Israel), English (Jamaica), English (Jersey), English (Kenya), English (Kiribati), English (Lesotho), English (Liberia), English (Macau SAR China), English (Madagascar), English (Malawi), English (Malaysia), English (Malta), English (Mauritius), English (Micronesia), English (Montserrat), English (Namibia), English (Nauru), English (Netherlands), English (New Zealand), English (Nigeria), English (Niue), English (Norfolk Island), English (Pakistan), English (Palau), English (Papua New Guinea), English (Philippines), English (Pitcairn Islands), English (Rwanda), English (Samoa), English (Seychelles), English (Sierra Leone), English (Singapore), English (Sint Maarten), English (Slovenia), English (Solomon Islands), English (South Sudan), English (St. Helena), English (St. Kitts & Nevis), English (St. Lucia), English (St. Vincent & Grenadines), English (Sudan), English (Swaziland), English (Switzerland), English (Tanzania), English (Tokelau), English (Tonga), English (Trinidad & Tobago), English (Turks & Caicos Islands), English (Tuvalu), English (Uganda), English (United Kingdom), English (Vanuatu), English (World), English (Zambia), English (Zimbabwe), Estonian, Estonian (Estonia), Ewondo, Ewondo (Cameroon), Faroese, Faroese (Denmark), Faroese (Faroe Islands), Finnish, Finnish (Finland), French, French (Algeria), French (Belgium), French (Benin), French (Burkina Faso), French (Burundi), French (Cameroon), French (Central African Republic), French (Chad), French (Comoros), French (Congo - Brazzaville), French (Congo - Kinshasa), French (Côte d’Ivoire), French (Djibouti), French (Equatorial Guinea), French (France), French (French Guiana), French (French Polynesia), French (Gabon), French (Guadeloupe), French (Guinea), French (Haiti), French (Luxembourg), French (Madagascar), French (Mali), French (Martinique), French (Mauritania), French (Mauritius), French (Mayotte), French (Monaco), French (Morocco), French (New Caledonia), French (Niger), French (Rwanda), French (Réunion), French (Senegal), French (Seychelles), French (St. Barthélemy), French (St. Martin), French (St. Pierre & Miquelon), French (Switzerland), French (Syria), French (Togo), French (Tunisia), French (Vanuatu), French (Wallis & Futuna), Friulian, Friulian (Italy), Fulah, Fulah (Cameroon), Fulah (Guinea), Fulah (Mauritania), Fulah (Senegal), Galician, Galician (Spain), Ganda, Ganda (Uganda), Georgian, Georgian (Georgia), German, German (Austria), German (Belgium), German (Germany), German (Italy), German (Liechtenstein), German (Luxembourg), German (Switzerland), Greek, Greek (Cyprus), Greek (Greece), Gujarati, Gujarati (India), Gusii, Gusii (Kenya), Hausa, Hausa (Ghana), Hausa (Niger), Hausa (Nigeria), Hawaiian, Hawaiian (United States), Hebrew, Hebrew (Israel), Hindi, Hindi (India), Icelandic, Icelandic (Iceland), Igbo, Igbo (Nigeria), Inari Sami, Inari Sami (Finland), Indonesian, Indonesian (Indonesia), Irish, Irish (Ireland), Italian, Italian (Italy), Italian (San Marino), Italian (Switzerland), Italian (Vatican City), Jola-Fonyi, Jola-Fonyi (Senegal), Kabuverdianu, Kabuverdianu (Cape Verde), Kabyle, Kabyle (Algeria), Kako, Kako (Cameroon), Kalenjin, Kalenjin (Kenya), Kamba, Kamba (Kenya), Kannada, Kannada (India), Kazakh, Kazakh (Kazakhstan), Khmer, Khmer (Cambodia), Kikuyu, Kikuyu (Kenya), Konkani, Konkani (India), Koyra Chiini, Koyra Chiini (Mali), Koyraboro Senni, Koyraboro Senni (Mali), Kwasio, Kwasio (Cameroon), Kyrgyz, Kyrgyz (Kyrgyzstan), Langi, Langi (Tanzania), Lao, Lao (Laos), Latvian, Latvian (Latvia), Lingala, Lingala (Angola), Lingala (Central African Republic), Lingala (Congo - Brazzaville), Lingala (Congo - Kinshasa), Lower Sorbian, Lower Sorbian (Germany), Luba-Katanga, Luba-Katanga (Congo - Kinshasa), Luo, Luo (Kenya), Luxembourgish, Luxembourgish (Luxembourg), Luyia, Luyia (Kenya), Macedonian, Macedonian (Macedonia), Machame, Machame (Tanzania), Makhuwa-Meetto, Makhuwa-Meetto (Mozambique), Makonde, Makonde (Tanzania), Malay, Malay (Brunei), Malay (Malaysia), Malay (Singapore), Malayalam, Malayalam (India), Maltese, Maltese (Malta), Marathi, Marathi (India), Masai, Masai (Kenya), Masai (Tanzania), Meru, Meru (Kenya), Morisyen, Morisyen (Mauritius), Mundang, Mundang (Cameroon), Nama, Nama (Namibia), Ngiemboon, Ngiemboon (Cameroon), North Ndebele, North Ndebele (Zimbabwe), Northern Sami (Finland), Norwegian, Norwegian (Norway), Norwegian (Norway, Nynorsk), Norwegian Bokmål, Norwegian Bokmål (Norway), Norwegian Bokmål (Svalbard & Jan Mayen), Norwegian Nynorsk, Norwegian Nynorsk (Norway), Nuer, Nuer (South Sudan), Nyankole, Nyankole (Uganda), Oromo, Oromo (Ethiopia), Oromo (Kenya), Ossetic, Ossetic (Georgia), Ossetic (Russia), Polish, Polish (Poland), Portuguese, Portuguese (Angola), Portuguese (Brazil), Portuguese (Cape Verde), Portuguese (Equatorial Guinea), Portuguese (Guinea-Bissau), Portuguese (Luxembourg), Portuguese (Macau SAR China), Portuguese (Mozambique), Portuguese (Portugal), Portuguese (Switzerland), Portuguese (São Tomé & Príncipe), Portuguese (Timor-Leste), Punjabi, Punjabi (Arabic), Punjabi (Arabic, Pakistan), Punjabi (Gurmukhi), Punjabi (Gurmukhi, India), Quechua, Quechua (Bolivia), Quechua (Ecuador), Quechua (Peru), Romanian, Romanian (Moldova), Romanian (Romania), Romansh, Romansh (Switzerland), Rombo, Rombo (Tanzania), Rundi, Rundi (Burundi), Russian, Russian (Belarus), Russian (Kazakhstan), Russian (Kyrgyzstan), Russian (Moldova), Russian (Russia), Russian (Ukraine), Rwa, Rwa (Tanzania), Samburu, Samburu (Kenya), Sango, Sango (Central African Republic), Sangu, Sangu (Tanzania), Scottish Gaelic, Scottish Gaelic (United Kingdom), Sena, Sena (Mozambique), Serbian, Serbian (Bosnia & Herzegovina), Serbian (Cyrillic), Serbian (Cyrillic, Bosnia & Herzegovina), Serbian (Cyrillic, Kosovo), Serbian (Cyrillic, Montenegro), Serbian (Cyrillic, Serbia), Serbian (Latin), Serbian (Latin, Bosnia & Herzegovina), Serbian (Latin, Kosovo), Serbian (Latin, Montenegro), Serbian (Latin, Serbia), Serbian (Montenegro), Serbian (Serbia and Montenegro), Serbian (Serbia), Shambala, Shambala (Tanzania), Slovak, Slovak (Slovakia), Slovenian, Slovenian (Slovenia), Soga, Soga (Uganda), Somali, Somali (Djibouti), Somali (Ethiopia), Somali (Kenya), Somali (Somalia), Spanish, Spanish (Argentina), Spanish (Belize), Spanish (Bolivia), Spanish (Brazil), Spanish (Canary Islands), Spanish (Ceuta & Melilla), Spanish (Chile), Spanish (Colombia), Spanish (Costa Rica), Spanish (Cuba), Spanish (Dominican Republic), Spanish (Ecuador), Spanish (El Salvador), Spanish (Equatorial Guinea), Spanish (Guatemala), Spanish (Honduras), Spanish (Latin America), Spanish (Mexico), Spanish (Nicaragua), Spanish (Paraguay), Spanish (Peru), Spanish (Philippines), Spanish (Spain), Spanish (United States), Spanish (Uruguay), Spanish (Venezuela), Standard Moroccan Tamazight, Standard Moroccan Tamazight (Morocco), Swahili, Swahili (Congo - Kinshasa), Swahili (Kenya), Swahili (Tanzania), Swahili (Uganda), Swedish (Finland), Swiss German, Swiss German (France), Swiss German (Liechtenstein), Swiss German (Switzerland), Tachelhit, Tachelhit (Latin), Tachelhit (Latin, Morocco), Tachelhit (Tifinagh), Tachelhit (Tifinagh, Morocco), Taita, Taita (Kenya), Tajik, Tajik (Tajikistan), Tamil, Tamil (India), Tamil (Malaysia), Tamil (Singapore), Tamil (Sri Lanka), Tasawaq, Tasawaq (Niger), Tatar, Tatar (Russia), Telugu, Telugu (India), Teso, Teso (Kenya), Teso (Uganda), Thai, Thai (Thailand), Thai (Thailand, TH, Thai Digits), Tigrinya, Tigrinya (Eritrea), Tigrinya (Ethiopia), Tongan, Tongan (Tonga), Turkish, Turkish (Cyprus), Turkish (Turkey), Turkmen, Turkmen (Turkmenistan), Ukrainian, Ukrainian (Ukraine), Upper Sorbian, Upper Sorbian (Germany), Urdu, Urdu (India), Urdu (Pakistan), Uzbek, Uzbek (Cyrillic), Uzbek (Cyrillic, Uzbekistan), Uzbek (Latin), Uzbek (Latin, Uzbekistan), Vai, Vai (Latin), Vai (Latin, Liberia), Vai (Vai), Vai (Vai, Liberia), Vietnamese, Vietnamese (Vietnam), Vunjo, Vunjo (Tanzania), Welsh, Welsh (United Kingdom), Western Frisian, Western Frisian (Netherlands), Wolof, Wolof (Senegal), Yangben, Yangben (Cameroon), Yiddish, Yiddish (World), Yoruba, Yoruba (Benin), Yoruba (Nigeria), Zarma, Zarma (Niger)]
dMyг = [Bulgarian, Bulgarian (Bulgaria)]
yMd = [, Afrikaans, Afrikaans (Namibia), Afrikaans (South Africa), Akan, Akan (Ghana), Basque, Basque (Spain), Cantonese, Cantonese (Simplified), Cantonese (Simplified, China), Cantonese (Traditional), Cantonese (Traditional, Hong Kong SAR China), Central Kurdish, Central Kurdish (Iran), Central Kurdish (Iraq), Chechen, Chechen (Russia), Chinese, Chinese (China), Chinese (Simplified), Chinese (Simplified, China), Chinese (Taiwan), Chinese (Traditional), Chinese (Traditional, Taiwan), Church Slavic, Church Slavic (Russia), Cornish, Cornish (United Kingdom), Dzongkha, Dzongkha (Bhutan), English (Canada), English (South Africa), English (Sweden), Esperanto, Esperanto (World), French (Canada), Hungarian, Hungarian (Hungary), Japanese, Japanese (Japan), Kalaallisut, Kalaallisut (Greenland), Kinyarwanda, Kinyarwanda (Rwanda), Korean, Korean (North Korea), Korean (South Korea), Lakota, Lakota (United States), Lithuanian, Lithuanian (Lithuania), Low German, Low German (Germany), Low German (Netherlands), Malagasy, Malagasy (Madagascar), Manx, Manx (Isle of Man), Mazanderani, Mazanderani (Iran), Metaʼ, Metaʼ (Cameroon), Mongolian, Mongolian (Mongolia), Nepali, Nepali (India), Nepali (Nepal), Ngomba, Ngomba (Cameroon), Northern Luri, Northern Luri (Iran), Northern Luri (Iraq), Northern Sami, Northern Sami (Norway), Northern Sami (Sweden), Pashto, Pashto (Afghanistan), Persian, Persian (Afghanistan), Persian (Iran), Prussian, Prussian (World), Sakha, Sakha (Russia), Shona, Shona (Zimbabwe), Sichuan Yi, Sichuan Yi (China), Sindhi, Sindhi (Pakistan), Sinhala, Sinhala (Sri Lanka), Swedish, Swedish (Sweden), Swedish (Åland Islands), Tibetan, Tibetan (China), Tibetan (India), Uyghur, Uyghur (China), Uzbek (Arabic), Uzbek (Arabic, Afghanistan), Volapük, Volapük (World), Walser, Walser (Switzerland)]
如果需要，您也可以消除G和r模式字母。代替replaceAll("\\P{L}", "")，使用replaceAll("[^yMd]", "")。
如果您更喜欢toUpperCase()，YMD和DMY之类的值，当然可以调用MDY。