DisplayedLanguage to languageTag using Locale?

Question

I use Locale and have displayed language in String, for example "English". Is it possible to convert it to language tag(en)?

Answer 1

tl;dr

No, localized names of languages are not mapped back to the standardized language code.

Language code leads to localized language name, but not vice versa.

Localized output, not input

Use localized text such as "English" for presentation to user only, not as key data.

We have international standards for precisely identifying human languages and cultures such as en for English & US for United States culture — use those as key data for purposes such as obtaining a Locale object.

For example:

• "English" (the word “English” in English)
• "anglais" (the word “English” in French)
• "անգլերեն" (the word “English” in Armenian)

… are outputs, not inputs.

This is the difference between Locale#getLanguage and Locale#getDisplayLanguage. The first returns a code while the second returns a localized name of that language. Ditto for Locale#getCountry and Locale#getDisplayCountry.

For fun, let's look at all possible names for “English”.

for ( Locale locale : Locale.getAvailableLocales() )
{
    System.out.println( Locale.US.getLanguage() + " ➜ " + Locale.US.getDisplayLanguage( locale ) + " in locale: " + locale.getDisplayName( Locale.US ) );
}

See this code run live at IdeOne.com.

Here is the partial results, truncated per the limit of an Answer's size in Stack Overflow.

en ➜ English in locale: 
en ➜ אנגלית in locale: Hebrew
en ➜ อังกฤษ in locale: Thai (Thai, Thailand)
en ➜ English in locale: Low German
en ➜ iňlis dili in locale: Turkmen (Latin, Turkmenistan)
en ➜ እንግሊዝ in locale: Tigrinya (Ethiopia)
en ➜ ஆங்கிலம் in locale: Tamil (Singapore)
en ➜ angļu in locale: Latvian
en ➜ English in locale: English (Niue)
en ➜ 英语 in locale: Chinese (Simplified, Singapore)
en ➜ 𞤉𞤲𞤺𞤭𞤤𞤫𞥅𞤪𞤫 in locale: Fulah (Adlam, Liberia)
en ➜ English in locale: English (Jamaica)
en ➜ yaman in locale: Kako
en ➜ eaŋgalsgiella in locale: Northern Sami (Latin, Norway)
en ➜ انگريزي in locale: Sindhi (Arabic)
en ➜ inglés in locale: Spanish (Bolivia)
en ➜ ཨིང་ལིཤ་ཁ in locale: Dzongkha (Bhutan)
en ➜ ইংলিস in locale: Manipuri
en ➜ ענגליש in locale: Yiddish
en ➜ engleski in locale: Bosnian (Bosnia & Herzegovina)
en ➜ engelšćina in locale: Lower Sorbian (Germany)
en ➜ Englesch in locale: Luxembourgish (Latin, Luxembourg)
en ➜ English in locale: English (Liberia)
en ➜ الإنجليزية in locale: Arabic (Chad)
en ➜ angličtina in locale: Czech
en ➜ Αγγλικά in locale: Greek
en ➜ Thok liŋli̱thni in locale: Nuer (Latin, South Sudan)
en ➜ Engels in locale: Afrikaans
en ➜ Engeleere in locale: Fulah (Latin, Mauritania)
en ➜ Kiingereza in locale: Swahili (Uganda)
en ➜ eŋgâlâskielâ in locale: Inari Sami
en ➜ iňlis dili in locale: Turkmen (Turkmenistan)
en ➜ енглески in locale: Serbian (Cyrillic, Montenegro)
en ➜ الإنجليزية in locale: Arabic (Egypt)
en ➜ engelšćina in locale: Lower Sorbian
en ➜ англисаг in locale: Ossetic (Cyrillic, Georgia)
en ➜ Èdè Gẹ̀ẹ́sì in locale: Yoruba (Nigeria)
en ➜ eaŋgalsgiella in locale: Northern Sami (Norway)
en ➜ Inglisi senni in locale: Koyra Chiini
en ➜ English in locale: English (Palau)
en ➜ angielski in locale: Polish (Poland)
en ➜ енглески in locale: Serbian (Serbia and Montenegro)
en ➜ अङ्ग्रेजी in locale: Nepali (India)
en ➜ Kɨŋgele in locale: Aghem (Latin, Cameroon)
en ➜ الإنجليزية in locale: Arabic (Western Sahara)
en ➜ engleski in locale: Bosnian (Latin, Bosnia & Herzegovina)
en ➜ English in locale: Low German (Germany)
en ➜ engelsk in locale: Norwegian Bokmål (Svalbard & Jan Mayen)
en ➜ inglés in locale: Spanish (United States)
en ➜ आङ्ग्लभाषा in locale: Sanskrit
en ➜ English in locale: English (United States, Computer)
en ➜ inglês in locale: Portuguese (Macao SAR China)
en ➜ 英语 in locale: Chinese (Simplified)
en ➜ Englesch in locale: Luxembourgish (Luxembourg)
en ➜ engelšćina in locale: Lower Sorbian (Latin, Germany)
en ➜ enska in locale: Icelandic (Latin, Iceland)
en ➜ Ingiriisi in locale: Somali (Kenya)
en ➜ Inglisi senni in locale: Zarma (Niger)
en ➜ անգլերեն in locale: Armenian (Armenian, Armenia)
en ➜ Engeleere in locale: Fulah (Latin, Ghana)
en ➜ anglais in locale: French (St. Pierre & Miquelon)
en ➜ الإنجليزية in locale: Arabic (Comoros)
en ➜ engelsk in locale: Norwegian (Norway, Nynorsk)
en ➜ angielski in locale: Polish (Latin, Poland)
en ➜ Kɨŋgele in locale: Aghem (Cameroon)
en ➜ અંગ્રેજી in locale: Gujarati (Gujarati, India)
en ➜ Kingereza in locale: Teso
en ➜ İngilizce in locale: Turkish (Turkey)
en ➜ ingeles in locale: Basque
en ➜ English in locale: Kalaallisut (Latin, Greenland)
en ➜ الإنجليزية in locale: Arabic (Mauritania)
en ➜ inglés in locale: Spanish (Dominican Republic)
en ➜ английский in locale: Russian
en ➜ ingilis in locale: Azerbaijani
en ➜ Inggris in locale: Sundanese (Latin)
en ➜ انگلیسی in locale: Persian
en ➜ English in locale: Kalaallisut (Greenland)
en ➜ English in locale: English (Nauru)
en ➜ isi-Ngisi in locale: North Ndebele
en ➜ ағылшын тілі in locale: Kazakh
en ➜ English in locale: Low German (Latin, Germany)
en ➜ Icyongereza in locale: Kinyarwanda (Latin, Rwanda)
en ➜ անգլերեն in locale: Armenian
en ➜ English in locale: English (Australia)
en ➜ English in locale: English (Cyprus)
en ➜ İngilizce in locale: Turkish (Latin, Turkey)
en ➜ እንግሊዝ in locale: Tigrinya (Eritrea)
en ➜ Thok liŋli̱thni in locale: Nuer (South Sudan)
en ➜ English in locale: English (Rwanda)
en ➜ Kiingeeza in locale: Shambala
en ➜ Kingereza in locale: Luo
en ➜ Englesch in locale: Luxembourgish
en ➜ engleski in locale: Croatian (Latin, Croatia)
en ➜ Inggris in locale: Sundanese
en ➜ lingɛlɛ́sa in locale: Lingala (Congo - Kinshasa)
en ➜ ngilísè in locale: Ngiemboon (Cameroon)
en ➜ engelsk in locale: Norwegian
en ➜ Inglisi senni in locale: Zarma (Latin, Niger)
en ➜ الإنجليزية in locale: Arabic (Israel)
en ➜ Ingilishi in locale: Makhuwa-Meetto
en ➜ ଇଂରାଜୀ in locale: Odia (India)
en ➜ انګليسي in locale: Pashto (Arabic, Afghanistan)
en ➜ ingilis in locale: Azerbaijani (Latin)
en ➜ ஆங்கிலம் in locale: Tamil
en ➜ Kɨɨngeréesa in locale: Langi
en ➜ الإنجليزية in locale: Arabic (Syria)
en ➜ Kingereza in locale: Luo (Latin, Kenya)
en ➜ riingɛrís in locale: Bafia (Cameroon)
en ➜ དབྱིན་ཇིའི་སྐད། in locale: Tibetan
en ➜ инглиз in locale: Tatar (Russia)
en ➜ Ingliffa in locale: Oromo (Kenya)
en ➜ English in locale: English (American Samoa)
en ➜ anglais in locale: French (Vanuatu)
en ➜ 英文 in locale: Chinese (Taiwan)
en ➜ انگريزي in locale: Sindhi (India)
en ➜ kutitab Uingeresa in locale: Kalenjin
en ➜ ngilísè in locale: Ngiemboon (Latin, Cameroon)
en ➜ अंग्रेज़ी in locale: Maithili
en ➜ inglês in locale: Portuguese (Mozambique)
en ➜ anglais in locale: French (Niger)
en ➜ inglês in locale: Friulian (Latin, Italy)
en ➜ inglés in locale: Asturian (Latin, Spain)
en ➜ Hiingereza in locale: Bena (Latin, Tanzania)
en ➜ Kiingeeza in locale: Shambala (Tanzania)
en ➜ အင်္ဂလိပ် in locale: Burmese (Myanmar, Myanmar (Burma))
en ➜ English in locale: English (Jersey)
en ➜ lingɛlɛ́sa in locale: Lingala (Central African Republic)
en ➜ inglizcha in locale: Uzbek (Afghanistan)
en ➜ engelsk in locale: Danish (Latin, Denmark)
en ➜ English in locale: English (Christmas Island)
en ➜ Borɔfo in locale: Akan (Latin, Ghana)
en ➜ English in locale: English (Austria)
en ➜ inglés in locale: Galician
en ➜ енглески in locale: Serbian (Cyrillic)
en ➜ 英文 in locale: Cantonese (Simplified, China)
en ➜ 𞤉𞤲𞤺𞤭𞤤𞤫𞥅𞤪𞤫 in locale: Fulah (Adlam)
en ➜ ಇಂಗ್ಲಿಷ್ in locale: Kannada (India)
en ➜ Béarla in locale: Irish
en ➜ Ingles Simi in locale: Quechua
en ➜ English in locale: English (Tanzania)
en ➜ English in locale: English (Puerto Rico)
en ➜ zah Anglofoŋ in locale: Mundang
en ➜ Inggris in locale: Javanese
en ➜ انګليسي in locale: Pashto
en ➜ Chirungu in locale: Shona
en ➜ អង់គ្លេស in locale: Khmer
en ➜ ⵜⴰⵏⴳⵍⵉⵣⵜ in locale: Standard Moroccan Tamazight
en ➜ anglais in locale: French (New Caledonia)
en ➜ inglés in locale: Spanish
en ➜ Aŋgɛlúshi in locale: Ngomba
en ➜ Beurla in locale: Scottish Gaelic (United Kingdom)
en ➜ Änglisch in locale: Swiss German
en ➜ anglais in locale: French (Cameroon)
en ➜ Engliš in locale: Walser (Latin, Switzerland)
en ➜ ਅੰਗਰੇਜ਼ੀ in locale: Punjabi (Gurmukhi, India)
en ➜ انگریزی in locale: Urdu (Arabic, Pakistan)
en ➜ Ínglish in locale: Nigerian Pidgin (Latin, Nigeria)
en ➜ Kingereza in locale: Teso (Uganda)
en ➜ Ingles in locale: Cebuano
en ➜ engelsk in locale: Norwegian (Latin, Norway)
en ➜ ইংরেজি in locale: Bangla (Bangla, Bangladesh)
en ➜ eŋgâlâskielâ in locale: Inari Sami (Latin, Finland)
en ➜ English in locale: English (Netherlands)
en ➜ lingɛlɛ́sa in locale: Lingala (Congo - Brazzaville)
en ➜ अङ्ग्रेजी in locale: Nepali (Devanagari, Nepal)
en ➜ ఇంగ్లీష్ in locale: Telugu
en ➜ ingilis in locale: Azerbaijani (Azerbaijan)
en ➜ angleščina in locale: Slovenian
en ➜ Αγγλικά in locale: Greek (Cyprus)
en ➜ इंग्रजी in locale: Marathi (India)
en ➜ îngilîzî in locale: Kurdish (Turkey)
en ➜ Turanci in locale: Hausa
en ➜ Kingereza in locale: Gusii (Latin, Kenya)
en ➜ ئینگیلیسی in locale: Northern Luri (Iran)
en ➜ Änglisch in locale: Swiss German (France)
en ➜ inglés in locale: Spanish (Honduras)
en ➜ angol in locale: Hungarian (Hungary)
en ➜ Engeleere in locale: Fulah (Senegal)
en ➜ Ishingelesa in locale: Sangu
en ➜ anglisht in locale: Albanian (North Macedonia)
en ➜ енглески in locale: Serbian (Cyrillic, Bosnia & Herzegovina)
en ➜ английски in locale: Bulgarian (Cyrillic, Bulgaria)
en ➜ Ingiriisi in locale: Somali (Latin, Somalia)
en ➜ inglise in locale: Estonian (Estonia)
en ➜ Kiingereza in locale: Swahili
en ➜ الإنجليزية in locale: Arabic (Oman)
en ➜ Ingelsk in locale: Western Frisian (Netherlands)
en ➜ Ngɛ̄lɛ̄n in locale: Kwasio
en ➜ İngilizce in locale: Turkish (Cyprus)
en ➜ angļu in locale: Latvian (Latin, Latvia)
en ➜ inglizcha in locale: Uzbek (Latin, Uzbekistan)
en ➜ ئینگیلیسی in locale: Northern Luri (Iraq)
en ➜ English in locale: Duala (Cameroon)
en ➜ Englisch in locale: German (Italy)
en ➜ inglês in locale: Portuguese (Latin, Brazil)
en ➜ ꕶꕱ in locale: Vai (Vai)
en ➜ anglais in locale: French (Tunisia)
en ➜ енглески in locale: Serbian (Serbia)
en ➜ Englisch in locale: German (Switzerland)
en ➜ Kiingereza in locale: Swahili (Latin, Tanzania)
en ➜ anglais in locale: French (French Polynesia)
en ➜ inglês in locale: Portuguese (Equatorial Guinea)
en ➜ અંગ્રેજી in locale: Gujarati
en ➜ Kyingereza in locale: Vunjo (Tanzania)
en ➜ Kyingereza in locale: Machame (Tanzania)
en ➜ Anglisy in locale: Malagasy (Latin, Madagascar)
en ➜ English in locale: English (Tuvalu)
en ➜ ອັງກິດ in locale: Lao
en ➜ English in locale: English (Pitcairn Islands)
en ➜ Lingelesa in locale: Luba-Katanga (Latin, Congo - Kinshasa)
en ➜ 英语 in locale: Chinese (Simplified, Hong Kong SAR China)
en ➜ Engels in locale: Dutch (Netherlands)
en ➜ English in locale: English (Guyana)
en ➜ engleski in locale: Bosnian (Latin)
en ➜ angle in locale: Jola-Fonyi (Senegal)
en ➜ англисаг in locale: Ossetic
en ➜ Engels in locale: Dutch (Curaçao)
en ➜ الإنجليزية in locale: Arabic (Algeria)
en ➜ inglês in locale: Portuguese (Switzerland)
en ➜ anglais in locale: French (Equatorial Guinea)
en ➜ እንግሊዝኛ in locale: Amharic
en ➜ English in locale: English (Nigeria)
en ➜ anglais in locale: French (Côte d’Ivoire)
en ➜ Gĩthungũ in locale: Kikuyu (Kenya)
en ➜ anglese in locale: Interlingua (world)
en ➜ English in locale: English (Pakistan)
en ➜ 英语 in locale: Chinese (China)
en ➜ English in locale: English (St. Lucia)
en ➜ Icyongereza in locale: Kinyarwanda
en ➜ अंग्रेज़ी in locale: Bodo (India)
en ➜ 𞤉𞤲𞤺𞤭𞤤𞤫𞥅𞤪𞤫 in locale: Fulah (Adlam, Burkina Faso)
en ➜ English in locale: Manx (Isle of Man)
en ➜ English in locale: Cornish (Latin, United Kingdom)
en ➜ angilɛkan in locale: Bambara (Latin, Mali)
en ➜ íŋgilísé in locale: Yangben (Latin, Cameroon)
en ➜ англиски in locale: Macedonian (North Macedonia)
en ➜ English in locale: English (Trinidad & Tobago)
en ➜ Kingereza in locale: Taita
en ➜ angleščina in locale: Slovenian (Slovenia)
en ➜ Anglëe in locale: Sango (Latin, Central African Republic)
en ➜ Inglisi senni in locale: Koyraboro Senni
en ➜ englanti in locale: Finnish (Latin, Finland)
en ➜ English in locale: Xhosa (South Africa)
en ➜ anglais in locale: French (Belgium)
en ➜ Aŋgɛlúshi in locale: Ngomba (Cameroon)
en ➜ 𞤉𞤲𞤺𞤭𞤤𞤫𞥅𞤪𞤫 in locale: Fulah (Adlam, Niger)
en ➜ inglés in locale: Spanish (Venezuela)
en ➜ Kĩngeretha in locale: Meru (Kenya)
en ➜ Anglisy in locale: Malagasy
en ➜ इंग्रजी in locale: Marathi
en ➜ English in locale: English (Bermuda)
en ➜ engelsk in locale: Norwegian Bokmål (Norway)
en ➜ inglês in locale: Sena
en ➜ ingles in locale: Kabuverdianu (Cape Verde)
en ➜ English in locale: Metaʼ
en ➜ Tiếng Anh in locale: Vietnamese (Vietnam)
en ➜ English in locale: English (United States)
en ➜ angle in locale: Morisyen (Mauritius)
en ➜ anglais in locale: French (Burkina Faso)
en ➜ ਅੰਗਰੇਜ਼ੀ in locale: Punjabi (Gurmukhi)
en ➜ inglese in locale: Italian (San Marino)
en ➜ انگلیسی in locale: Persian (Arabic, Iran)
en ➜ आङ्ग्लभाषा in locale: Sanskrit (Devanagari, India)
en ➜ anglais in locale: French (Mayotte)
en ➜ અંગ્રેજી in locale: Gujarati (India)
en ➜ Engeleere in locale: Fulah (Latin, Cameroon)
en ➜ inglés in locale: Asturian
en ➜ Ingliż in locale: Maltese (Latin, Malta)
en ➜ englanti in locale: Finnish (Finland)
en ➜ 英文 in locale: Cantonese (Simplified)
en ➜ anglès in locale: Catalan (France)
en ➜ engleski in locale: Serbian (Latin, Bosnia & Herzegovina)
en ➜ 𑄃𑄨𑄁𑄢𑄨𑄎𑄨 in locale: Chakma (Chakma, Bangladesh)
en ➜ англійська in locale: Ukrainian (Cyrillic, Ukraine)
en ➜ anglais in locale: French (Djibouti)
en ➜ اَنگیٖزۍ in locale: Kashmiri (Arabic)
en ➜ 𞤉𞤲𞤺𞤭𞤤𞤫𞥅𞤪𞤫 in locale: Fulah (Adlam, Guinea-Bissau)
en ➜ Turanci in locale: Hausa (Ghana)
en ➜ ענגליש in locale: Yiddish (Hebrew, world)
en ➜ Engels in locale: Afrikaans (Latin, South Africa)
en ➜ እንግሊዝ in locale: Tigrinya (Ethiopic, Ethiopia)
en ➜ lea fakapālangi in locale: Tongan (Latin, Tonga)
en ➜ Englisch in locale: German (Belgium)
en ➜ እንግሊዝኛ in locale: Amharic (Ethiopic, Ethiopia)
en ➜ Engeleere in locale: Fulah (Latin, Guinea-Bissau)
en ➜ Orungyereza in locale: Chiga
en ➜ 英文 in locale: Chinese (Macao SAR China)
en ➜ zah Anglofoŋ in locale: Mundang (Latin, Cameroon)
en ➜ Orungyereza in locale: Nyankole (Uganda)
en ➜ Inggeris in locale: Malay (Malaysia)
en ➜ Icongereza in locale: Rundi (Latin, Burundi)
en ➜ ஆங்கிலம் in locale: Tamil (Sri Lanka)
en ➜ riingɛrís in locale: Bafia
en ➜ Englisch in locale: German (Latin, Germany)
en ➜ Saesneg in locale: Welsh
en ➜ Ingles in locale: Cebuano (Philippines)
en ➜ anglisht in locale: Albanian
en ➜ anglais in locale: French
en ➜ англисӣ in locale: Tajik (Tajikistan)
en ➜ Kyingereza in locale: Vunjo (Latin, Tanzania)
en ➜ Ingles Simi in locale: Quechua (Peru)
en ➜ Englisch in locale: German
en ➜ inglés in locale: Spanish (Ecuador)
en ➜ англиски in locale: Macedonian (Cyrillic, North Macedonia)
en ➜ 𞤉𞤲𞤺𞤭𞤤𞤫𞥅𞤪𞤫 in locale: Fulah (Adlam, Cameroon)
en ➜ Lungereza in locale: Ganda (Uganda)
en ➜ Engeleere in locale: Fulah (Latin, Niger)
en ➜ i-English in locale: Zulu (South Africa)
en ➜ anglais in locale: French (Latin, France)
en ➜ Inggris in locale: Sundanese (Latin, Indonesia)
en ➜ Orungyereza in locale: Chiga (Uganda)
en ➜ Änglesch in locale: Colognian (Germany)
en ➜ Lungereza in locale: Ganda
en ➜ английский in locale: Russian (Russia)
en ➜ Ínglish in locale: Nigerian Pidgin (Nigeria)
en ➜ English in locale: English (Dominica)
en ➜ انگريزي in locale: Sindhi
en ➜ אנגלית in locale: Hebrew (Hebrew, Israel)
en ➜ Béarla in locale: Irish (Ireland)
en ➜ English in locale: English (Burundi)
en ➜ 英文 in locale: Cantonese (China)
en ➜ englais in locale: Romansh (Latin, Switzerland)
en ➜ English in locale: English (Samoa)
en ➜ anglais in locale: French (Luxembourg)
en ➜ Ingiriisi in locale: Somali
en ➜ Ingarihi in locale: Maori (New Zealand)
en ➜ الإنجليزية in locale: Arabic (Eritrea)
en ➜ Taglizit in locale: Kabyle
en ➜ Thok liŋli̱thni in locale: Nuer
en ➜ Chirungu in locale: Shona (Zimbabwe)
en ➜ inglés in locale: Spanish (Ceuta & Melilla)
en ➜ Béarla in locale: Irish (United Kingdom)
en ➜ อังกฤษ in locale: Thai (Thailand, TH, Thai Digits)
en ➜ अंग्रेज़ी in locale: Hindi
en ➜ anglais in locale: French (Seychelles)
en ➜ English in locale: English (Sierra Leone)
en ➜ Engeleere in locale: Fulah (Latin, Nigeria)
en ➜ engelsk in locale: Norwegian (Norway)
en ➜ 𞤉𞤲𞤺𞤭𞤤𞤫𞥅𞤪𞤫 in locale: Fulah (Adlam, Nigeria)
en ➜ 英文 in locale: Chinese (Traditional, Macao SAR China)
en ➜ English in locale: English (St. Helena)
en ➜ ꕶꕱ in locale: Vai
en ➜ انگريزي in locale: Sindhi (Arabic, Pakistan)
en ➜ Englisch in locale: German (Luxembourg)
en ➜ Ingarihi in locale: Maori
en ➜ Ingliż in locale: Maltese
en ➜ Englisch in locale: German (Germany)
en ➜ engelsk in locale: Norwegian Nynorsk (Latin, Norway)
en ➜ English in locale: English (Denmark)
en ➜ íŋgilísé in locale: Yangben
en ➜ Ingiriisi in locale: Somali (Djibouti)
en ➜ anglų in locale: Lithuanian (Lithuania)
en ➜ Kingereza in locale: Kamba
en ➜ engleză in locale: Romanian
en ➜ angla in locale: Esperanto (world)
en ➜ انګليسي in locale: Pashto (Pakistan)
en ➜ Yevugbe in locale: Ewe
en ➜ English in locale: English (U.S. Outlying Islands)
en ➜ English in locale: English (Slovenia)
en ➜ ꕶꕱ in locale: Vai (Vai, Liberia)
en ➜ ອັງກິດ in locale: Lao (Laos)
en ➜ ᎩᎵᏏ in locale: Cherokee
en ➜ Kiingereza in locale: Rombo (Latin, Tanzania)
en ➜ الإنجليزية in locale: Arabic (Lebanon)
en ➜ ئینگیلیسی in locale: Northern Luri (Arabic, Iran)
en ➜ Engels in locale: Afrikaans (South Africa)
en ➜ अंगरेजी in locale: Dogri
en ➜ Engeleere in locale: Fulah (Guinea)
en ➜ Änglesch in locale: Colognian (Latin, Germany)
en ➜ inglés in locale: Spanish (Belize)
en ➜ الإنجليزية in locale: Arabic (United Arab Emirates)
en ➜ angla in locale: Esperanto (Latin, world)
en ➜ engleski in locale: Croatian (Croatia)
en ➜ Kiingereza in locale: Rombo (Tanzania)
en ➜ ইংৰাজী in locale: Assamese
en ➜ inglese in locale: Italian
en ➜ اَنگیٖزۍ in locale: Kashmiri (India)
en ➜ အင်္ဂလိပ် in locale: Burmese (Myanmar (Burma))
en ➜ англи in locale: Mongolian (Mongolia)
en ➜ انگریزی in locale: Urdu (Pakistan)
en ➜ engelsk in locale: Danish (Denmark)
en ➜ English in locale: English (Micronesia)
en ➜ English in locale: English (Belgium)
en ➜ ꑱꇩꉙ in locale: Sichuan Yi
en ➜ anglais in locale: French (Wallis & Futuna)
en ➜ انگلیسی in locale: Mazanderani (Iran)
en ➜ Engels in locale: Nama
en ➜ English in locale: English (Singapore)
en ➜ kutitab Uingeresa in locale: Kalenjin (Kenya)
en ➜ Tanglizt in locale: Central Atlas Tamazight
en ➜ Engeleere in locale: Fulah (Latin, Gambia)
en ➜ инглиз in locale: Tatar (Cyrillic, Russia)
en ➜ Kingereza in locale: Teso (Latin, Uganda)
en ➜ inglês in locale: Friulian
en ➜ Ingliffa in locale: Oromo
en ➜ Kiingeredha in locale: Asu (Latin, Tanzania)
en ➜ Hiingereza in locale: Bena (Tanzania)
en ➜ Engeleere in locale: Fulah (Latin, Guinea)
en ➜ angleščina in locale: Slovenian (Latin, Slovenia)
en ➜ English in locale: English (Sudan)
en ➜ अंग्रेज़ी in locale: Maithili (Devanagari, India)
en ➜ 英語 in locale: Japanese (Japan, JP, Japanese Calendar)
en ➜ inglés in locale: Spanish (El Salvador)
en ➜ inglês in locale: Portuguese (Brazil)
en ➜ ইংলিস in locale: Manipuri (Bangla, India)
en ➜ ഇംഗ്ലീഷ് in locale: Malayalam (India)
en ➜ Béarla in locale: Irish (Latin, Ireland)
en ➜ English in locale: English (Falkland Islands)
en ➜ enska in locale: Icelandic (Iceland)
en ➜ Hɔp u ŋgisì in locale: Basaa (Latin, Cameroon)
en ➜ English in locale: English (Diego Garcia)
en ➜ engleski in locale: Croatian
en ➜ inglês in locale: Portuguese (São Tomé & Príncipe)
en ➜ Borɔfo in locale: Akan (Ghana)
en ➜ anglų in locale: Lithuanian
en ➜ English in locale: Uzbek (Arabic, Afghanistan)
en ➜ 𑄃𑄨𑄁𑄢𑄨𑄎𑄨 in locale: Chakma
en ➜ English in locale: English (Sweden)
en ➜ 英语 in locale: Chinese (Simplified, China)
en ➜ inglés in locale: Spanish (Latin America)
en ➜ lingɛlɛ́sa in locale: Lingala (Latin, Congo - Kinshasa)
en ➜ yaman in locale: Kako (Latin, Cameroon)
en ➜ English in locale: English
en ➜ Kingereza in locale: Gusii (Kenya)
en ➜ Änglisch in locale: Swiss German (Liechtenstein)
en ➜ 𑄃𑄨𑄁𑄢𑄨𑄎𑄨 in locale: Chakma (Bangladesh)
en ➜ inglés in locale: Spanish (Canary Islands)
en ➜ anglès in locale: Catalan
en ➜ الإنجليزية in locale: Arabic (Tunisia)
en ➜ angilɛkan in locale: Bambara (Mali)
en ➜ English in locale: Cornish (United Kingdom)
en ➜ ਅੰਗਰੇਜ਼ੀ in locale: Punjabi (Pakistan)
en ➜ ئىنگلىزچە in locale: Uyghur (China)
en ➜ Kyingereza in locale: Machame (Latin, Tanzania)
en ➜ Gĩthungũ in locale: Kikuyu (Latin, Kenya)
en ➜ inglés in locale: Spanish (Brazil)
en ➜ Inglisi senni in locale: Koyra Chiini (Mali)
en ➜ English in locale: English (Solomon Islands)
en ➜ དབྱིན་ཇིའི་སྐད། in locale: Tibetan (Tibetan, China)
en ➜ ᎩᎵᏏ in locale: Cherokee (United States)
en ➜ Icyongereza in locale: Kinyarwanda (Rwanda)
en ➜ ⵜⴰⵏⴳⵍⵉⵣⵜ in locale: Tachelhit (Tifinagh, Morocco)
en ➜ الإنجليزية in locale: Arabic (Iraq)
en ➜ Orungyereza in locale: Nyankole
en ➜ англиски in locale: Macedonian
en ➜ ᱟᱝᱜᱽᱨᱮᱡᱤ in locale: Santali
en ➜ English in locale: Punjabi (Arabic)
en ➜ English in locale: English (Germany)
en ➜ engleză in locale: Romanian (Moldova)
en ➜ engleski in locale: Bosnian
en ➜ English in locale: English (Finland)
en ➜ Ingelsk in locale: Western Frisian
en ➜ อังกฤษ in locale: Thai
en ➜ inglizcha in locale: Uzbek (Uzbekistan)
en ➜ Kingereza in locale: Taita (Kenya)
en ➜ anglese in locale: Interlingua (Latin, world)
en ➜ Ааҥыллыы in locale: Sakha (Cyrillic, Russia)
en ➜ English in locale: English (Seychelles)
en ➜ English in locale: English (Uganda)
en ➜ English in locale: English (New Zealand)
en ➜ Inglisi senni in locale: Zarma
en ➜ inglés in locale: Spanish (Uruguay)
en ➜ nkʉtʉ́k ɔ́ɔ̄ nkɨ́resa in locale: Masai (Kenya)
en ➜ ইংলিস in locale: Manipuri (India)
en ➜ английский in locale: Russian (Ukraine)
en ➜ Anglëe in locale: Sango (Central African Republic)
en ➜ English in locale: English (Fiji)
en ➜ Englisch in locale: German (Liechtenstein)
en ➜ English in locale: English (Barbados)
en ➜ eŋgâlâskielâ in locale: Inari Sami (Finland)
en ➜ engleski in locale: Croatian (Bosnia & Herzegovina)
en ➜ Èdè Gẹ̀ẹ́sì in locale: Yoruba (Latin, Nigeria)
en ➜ Englisch in locale: German (Austria)
en ➜ Lingelesa in locale: Luba-Katanga (Congo - Kinshasa)
en ➜ الإنجليزية in locale: Arabic (world)
en ➜ Ingiriisi in locale: Somali (Somalia)
en ➜ angļu in locale: Latvian (Latvia)
en ➜ ئینگلیزی in locale: Central Kurdish
en ➜ الإنجليزية in locale: Arabic (Kuwait)
en ➜ енглески in locale: Serbian (Cyrillic, Serbia)
en ➜ Ichi Sungu in locale: Bemba
en ➜ engelsk in locale: Danish
en ➜ Engliš in locale: Walser
en ➜ English in locale: English (Lesotho)
en ➜ Bekee in locale: Igbo
en ➜ English in locale: English (Hong Kong SAR China)
en ➜ अंग्रेज़ी in locale: Bodo (Devanagari, India)
en ➜ Kĩngeretha in locale: Meru (Latin, Kenya)
en ➜ ингалсан in locale: Chechen (Russia)
en ➜ ინგლისური in locale: Georgian (Georgia)
en ➜ Kiingereza in locale: Swahili (Tanzania)
en ➜ anglais in locale: French (Rwanda)
en ➜ Anglisy in locale: Malagasy (Madagascar)
en ➜ English in locale: English (Latin, United States)
en ➜ англисаг in locale: Ossetic (Russia)
en ➜ engleski in locale: Serbian (Latin, Serbia)
en ➜ англисче in locale: Kyrgyz (Kyrgyzstan)
en ➜ Tanglizt in locale: Central Atlas Tamazight (Latin, Morocco)
en ➜ Engels in locale: Dutch (Latin, Netherlands)
en ➜ îngilîzî in locale: Kurdish (Latin, Turkey)
en ➜ Gĩthungũ in locale: Kikuyu
en ➜ angle in locale: Morisyen (Latin, Mauritius)
en ➜ engelsk in locale: Norwegian Bokmål
en ➜ इंग्लीश in locale: Konkani
en ➜ Ǹkɔ́bɔ éngəlís in locale: Ewondo
en ➜ engelsk in locale: Norwegian Nynorsk
en ➜ الإنجليزية in locale: Arabic (Jordan)
en ➜ inglés in locale: Galician (Latin, Spain)
en ➜ английски in locale: Bulgarian
en ➜ ingles in locale: Kabuverdianu
en ➜ i-English in locale: Zulu
en ➜ англисче in locale: Kyrgyz (Cyrillic, Kyrgyzstan)
en ➜ እንግሊዝኛ in locale: Amharic (Ethiopia)
en ➜ anglais in locale: French (Algeria)
en ➜ དབྱིན་ཇིའི་སྐད། in locale: Tibetan (China)
en ➜ jendźelšćina in locale: Upper Sorbian
en ➜ Ingles Simi in locale: Quechua (Ecuador)
en ➜ ინგლისური in locale: Georgian (Georgian, Georgia)
en ➜ English in locale: English (Montserrat)
en ➜ इंग्लीश in locale: Konkani (Devanagari, India)
en ➜ English in locale: English (Guernsey)
en ➜ Chiingeleza in locale: Makonde (Latin, Tanzania)
en ➜ ᱟᱝᱜᱽᱨᱮᱡᱤ in locale: Santali (India)
en ➜ енглески in locale: Serbian (Montenegro)
en ➜ engelska in locale: Swedish (Sweden)
en ➜ Ínglish in locale: Nigerian Pidgin
en ➜ Ааҥыллыы in locale: Sakha
en ➜ Kĩngeretha in locale: Meru
en ➜ English in locale: English (Zambia)
en ➜ anglais in locale: French (Mali)
en ➜ Turanci in locale: Hausa (Nigeria)
en ➜ saozneg in locale: Breton
en ➜ الإنجليزية in locale: Arabic (Saudi Arabia)
en ➜ انگلیسی in locale: Persian (Afghanistan)
en ➜ Ingles in locale: Filipino (Latin, Philippines)
en ➜ angličtina in locale: Slovak
en ➜ Ingliffa in locale: Oromo (Latin, Ethiopia)
en ➜ англисаг in locale: Ossetic (Georgia)
en ➜ ئینگلیزی in locale: Central Kurdish (Arabic, Iraq)
en ➜ ענגליש in locale: Yiddish (world)
en ➜ ഇംഗ്ലീഷ് in locale: Malayalam
en ➜ English in locale: English (Malta)
en ➜ English in locale: English (Ghana)
en ➜ English in locale: English (Israel)
en ➜ engelska in locale: Swedish
en ➜ ಇಂಗ್ಲಿಷ್ in locale: Kannada (Kannada, India)
en ➜ Tanglizt in locale: Central Atlas Tamazight (Morocco)
en ➜ Αγγλικά in locale: Greek (Greek, Greece)
en ➜ Inglisi senni in locale: Koyraboro Senni (Mali)
en ➜ Kyingereza in locale: Rwa (Latin, Tanzania)
en ➜ Wašíčuiyapi in locale: Lakota (United States)
en ➜ अंगरेज़ी in locale: Sindhi (Devanagari)
en ➜ Poo in locale: Vai (Latin, Liberia)
en ➜ îngilîzî in locale: Kurdish
en ➜ Kiingereza in locale: Swahili (Congo - Kinshasa)
en ➜ 𞤉𞤲𞤺𞤭𞤤𞤫𞥅𞤪𞤫 in locale: Fulah (Adlam, Mauritania)
en ➜ Ingles in locale: Filipino (Philippines)
en ➜ inglese in locale: Italian (Vatican City)
en ➜ inglés in locale: Spanish (Philippines)
en ➜ inglés in locale: Spanish (Spain)
en ➜ inglés in locale: Spanish (Colombia)
en ➜ английски in locale: Bulgarian (Bulgaria)
en ➜ English in locale: English (St. Vincent & Grenadines)
en ➜ Inglisi senni in locale: Koyraboro Senni (Latin, Mali)
en ➜ Kɨŋgele in locale: Aghem
en ➜ jendźelšćina in locale: Upper Sorbian (Germany)
en ➜ ingeles in locale: Basque (Latin, Spain)
en ➜ English in locale: English (Europe)
en ➜ engelska in locale: Swedish (Latin, Sweden)
en ➜ الإنجليزية in locale: Arabic (Sudan)
en ➜ Turanci in locale: Hausa (Niger)
en ➜ English in locale: English (St. Kitts & Nevis)
en ➜ Kĩthungu in locale: Embu
en ➜ engleză in locale: Romanian (Romania)
en ➜ engleski in locale: Serbian (Latin, Montenegro)
en ➜ inglés in locale: Spanish (Guatemala)
en ➜ Engeleere in locale: Fulah (Latin, Liberia)
en ➜ Hɔp u ŋgisì in locale: Basaa (Cameroon)
en ➜ isi-Ngisi in locale: North Ndebele (Latin, Zimbabwe)
en ➜ anglais in locale: French (Madagascar)
en ➜ inglés in locale: Spanish (Chile)
en ➜ англи in locale: Mongolian
en ➜ Kingereza in locale: Kamba (Kenya)
en ➜ انگلیسی in locale: Persian (Iran)
en ➜ English in locale: English (Macao SAR China)
en ➜ 英語 in locale: Japanese (Japanese, Japan)
en ➜ Àngale in locale: Wolof
en ➜ ⵜⴰⵏⴳⵍⵉⵣⵜ in locale: Tachelhit (Tifinagh)
en ➜ English in locale: English (Belize)
en ➜ Wašíčuiyapi in locale: Lakota (Latin, United States)
en ➜ anglisht in locale: Albanian (Albania)
en ➜ engleză in locale: Romanian (Latin, Romania)
en ➜ Inglisi senni in locale: Tasawaq (Niger)
en ➜ Ngɛ̄lɛ̄n in locale: Kwasio (Cameroon)
en ➜ ஆங்கிலம் in locale: Tamil (Tamil, India)
en ➜ Taglizit in locale: Kabyle (Latin, Algeria)
en ➜ инҝилис in locale: Azerbaijani (Cyrillic)
en ➜ English in locale: English (Northern Mariana Islands)
en ➜ English in locale: English (Grenada)
en ➜ iňlis dili in locale: Turkmen
en ➜ Ishingelesa in locale: Sangu (Latin, Tanzania)
en ➜ Tanglizt in locale: Tachelhit (Latin)
en ➜ English in locale: English (Botswana)
en ➜ Taglizit in locale: Kabyle (Algeria)
en ➜ אנגלית in locale: Hebrew (Israel)
en ➜ Chiingeleza in locale: Makonde (Tanzania)
en ➜ ஆங்கிலம் in locale: Tamil (Malaysia)
en ➜ engelska in locale: Swedish (Finland)
en ➜ isi-Ngisi in locale: North Ndebele (Zimbabwe)
en ➜ Lusungu in locale: Luyia (Latin, Kenya)
en ➜ ইংলিস in locale: Manipuri (Bangla)
en ➜ अङ्ग्रेजी in locale: Nepali
en ➜ English in locale: English (Ireland)
en ➜ 英语 in locale: Chinese (Singapore)
en ➜ ඉංග්‍රීසි in locale: Sinhala (Sinhala, Sri Lanka)
en ➜ English in locale: English (Kiribati)
en ➜ Inglisi senni in locale: Tasawaq (Latin, Niger)
en ➜ Ingliffa in locale: Oromo (Ethiopia)
en ➜ ອັງກິດ in locale: Lao (Lao, Laos)
…

Answer 2

The method Locale.getLanguage gives it

Locale l = Locale.ENGLISH;
System.out.println(l.getLanguage()); // en