how to get country phone prefix from iso

I found a place where I can get the mapping in csv file. check here.

Also, I changed it into a class that translate the country code into phone prefix. here it is:

public class Iso2Phone {
public static String getPhone(String code) {
    return country2phone.get(code.toUpperCase());
}
public static Map<String, String> getAll(){
    return country2phone;
}
private static Map<String, String> country2phone = new HashMap<String, String>();
static {
    country2phone.put("AF", "+93");
    country2phone.put("AL", "+355");
    country2phone.put("DZ", "+213");
    country2phone.put("AD", "+376");
    country2phone.put("AO", "+244");
    country2phone.put("AG", "+1-268");
    country2phone.put("AR", "+54");
    country2phone.put("AM", "+374");
    country2phone.put("AU", "+61");
    country2phone.put("AT", "+43");
    country2phone.put("AZ", "+994");
    country2phone.put("BS", "+1-242");
    country2phone.put("BH", "+973");
    country2phone.put("BD", "+880");
    country2phone.put("BB", "+1-246");
    country2phone.put("BY", "+375");
    country2phone.put("BE", "+32");
    country2phone.put("BZ", "+501");
    country2phone.put("BJ", "+229");
    country2phone.put("BT", "+975");
    country2phone.put("BO", "+591");
    country2phone.put("BA", "+387");
    country2phone.put("BW", "+267");
    country2phone.put("BR", "+55");
    country2phone.put("BN", "+673");
    country2phone.put("BG", "+359");
    country2phone.put("BF", "+226");
    country2phone.put("BI", "+257");
    country2phone.put("KH", "+855");
    country2phone.put("CM", "+237");
    country2phone.put("CA", "+1");
    country2phone.put("CV", "+238");
    country2phone.put("CF", "+236");
    country2phone.put("TD", "+235");
    country2phone.put("CL", "+56");
    country2phone.put("CN", "+86");
    country2phone.put("CO", "+57");
    country2phone.put("KM", "+269");
    country2phone.put("CD", "+243");
    country2phone.put("CG", "+242");
    country2phone.put("CR", "+506");
    country2phone.put("CI", "+225");
    country2phone.put("HR", "+385");
    country2phone.put("CU", "+53");
    country2phone.put("CY", "+357");
    country2phone.put("CZ", "+420");
    country2phone.put("DK", "+45");
    country2phone.put("DJ", "+253");
    country2phone.put("DM", "+1-767");
    country2phone.put("DO", "+1-809and1-829");
    country2phone.put("EC", "+593");
    country2phone.put("EG", "+20");
    country2phone.put("SV", "+503");
    country2phone.put("GQ", "+240");
    country2phone.put("ER", "+291");
    country2phone.put("EE", "+372");
    country2phone.put("ET", "+251");
    country2phone.put("FJ", "+679");
    country2phone.put("FI", "+358");
    country2phone.put("FR", "+33");
    country2phone.put("GA", "+241");
    country2phone.put("GM", "+220");
    country2phone.put("GE", "+995");
    country2phone.put("DE", "+49");
    country2phone.put("GH", "+233");
    country2phone.put("GR", "+30");
    country2phone.put("GD", "+1-473");
    country2phone.put("GT", "+502");
    country2phone.put("GN", "+224");
    country2phone.put("GW", "+245");
    country2phone.put("GY", "+592");
    country2phone.put("HT", "+509");
    country2phone.put("HN", "+504");
    country2phone.put("HU", "+36");
    country2phone.put("IS", "+354");
    country2phone.put("IN", "+91");
    country2phone.put("ID", "+62");
    country2phone.put("IR", "+98");
    country2phone.put("IQ", "+964");
    country2phone.put("IE", "+353");
    country2phone.put("IL", "+972");
    country2phone.put("IT", "+39");
    country2phone.put("JM", "+1-876");
    country2phone.put("JP", "+81");
    country2phone.put("JO", "+962");
    country2phone.put("KZ", "+7");
    country2phone.put("KE", "+254");
    country2phone.put("KI", "+686");
    country2phone.put("KP", "+850");
    country2phone.put("KR", "+82");
    country2phone.put("KW", "+965");
    country2phone.put("KG", "+996");
    country2phone.put("LA", "+856");
    country2phone.put("LV", "+371");
    country2phone.put("LB", "+961");
    country2phone.put("LS", "+266");
    country2phone.put("LR", "+231");
    country2phone.put("LY", "+218");
    country2phone.put("LI", "+423");
    country2phone.put("LT", "+370");
    country2phone.put("LU", "+352");
    country2phone.put("MK", "+389");
    country2phone.put("MG", "+261");
    country2phone.put("MW", "+265");
    country2phone.put("MY", "+60");
    country2phone.put("MV", "+960");
    country2phone.put("ML", "+223");
    country2phone.put("MT", "+356");
    country2phone.put("MH", "+692");
    country2phone.put("MR", "+222");
    country2phone.put("MU", "+230");
    country2phone.put("MX", "+52");
    country2phone.put("FM", "+691");
    country2phone.put("MD", "+373");
    country2phone.put("MC", "+377");
    country2phone.put("MN", "+976");
    country2phone.put("ME", "+382");
    country2phone.put("MA", "+212");
    country2phone.put("MZ", "+258");
    country2phone.put("MM", "+95");
    country2phone.put("NA", "+264");
    country2phone.put("NR", "+674");
    country2phone.put("NP", "+977");
    country2phone.put("NL", "+31");
    country2phone.put("NZ", "+64");
    country2phone.put("NI", "+505");
    country2phone.put("NE", "+227");
    country2phone.put("NG", "+234");
    country2phone.put("NO", "+47");
    country2phone.put("OM", "+968");
    country2phone.put("PK", "+92");
    country2phone.put("PW", "+680");
    country2phone.put("PA", "+507");
    country2phone.put("PG", "+675");
    country2phone.put("PY", "+595");
    country2phone.put("PE", "+51");
    country2phone.put("PH", "+63");
    country2phone.put("PL", "+48");
    country2phone.put("PT", "+351");
    country2phone.put("QA", "+974");
    country2phone.put("RO", "+40");
    country2phone.put("RU", "+7");
    country2phone.put("RW", "+250");
    country2phone.put("KN", "+1-869");
    country2phone.put("LC", "+1-758");
    country2phone.put("VC", "+1-784");
    country2phone.put("WS", "+685");
    country2phone.put("SM", "+378");
    country2phone.put("ST", "+239");
    country2phone.put("SA", "+966");
    country2phone.put("SN", "+221");
    country2phone.put("RS", "+381");
    country2phone.put("SC", "+248");
    country2phone.put("SL", "+232");
    country2phone.put("SG", "+65");
    country2phone.put("SK", "+421");
    country2phone.put("SI", "+386");
    country2phone.put("SB", "+677");
    country2phone.put("SO", "+252");
    country2phone.put("ZA", "+27");
    country2phone.put("ES", "+34");
    country2phone.put("LK", "+94");
    country2phone.put("SD", "+249");
    country2phone.put("SR", "+597");
    country2phone.put("SZ", "+268");
    country2phone.put("SE", "+46");
    country2phone.put("CH", "+41");
    country2phone.put("SY", "+963");
    country2phone.put("TJ", "+992");
    country2phone.put("TZ", "+255");
    country2phone.put("TH", "+66");
    country2phone.put("TL", "+670");
    country2phone.put("TG", "+228");
    country2phone.put("TO", "+676");
    country2phone.put("TT", "+1-868");
    country2phone.put("TN", "+216");
    country2phone.put("TR", "+90");
    country2phone.put("TM", "+993");
    country2phone.put("TV", "+688");
    country2phone.put("UG", "+256");
    country2phone.put("UA", "+380");
    country2phone.put("AE", "+971");
    country2phone.put("GB", "+44");
    country2phone.put("US", "+1");
    country2phone.put("UY", "+598");
    country2phone.put("UZ", "+998");
    country2phone.put("VU", "+678");
    country2phone.put("VA", "+379");
    country2phone.put("VE", "+58");
    country2phone.put("VN", "+84");
    country2phone.put("YE", "+967");
    country2phone.put("ZM", "+260");
    country2phone.put("ZW", "+263");
    country2phone.put("GE", "+995");
    country2phone.put("TW", "+886");
    country2phone.put("AZ", "+374-97");
    country2phone.put("CY", "+90-392");
    country2phone.put("MD", "+373-533");
    country2phone.put("SO", "+252");
    country2phone.put("GE", "+995");
    country2phone.put("CX", "+61");
    country2phone.put("CC", "+61");
    country2phone.put("NF", "+672");
    country2phone.put("NC", "+687");
    country2phone.put("PF", "+689");
    country2phone.put("YT", "+262");
    country2phone.put("GP", "+590");
    country2phone.put("GP", "+590");
    country2phone.put("PM", "+508");
    country2phone.put("WF", "+681");
    country2phone.put("CK", "+682");
    country2phone.put("NU", "+683");
    country2phone.put("TK", "+690");
    country2phone.put("GG", "+44");
    country2phone.put("IM", "+44");
    country2phone.put("JE", "+44");
    country2phone.put("AI", "+1-264");
    country2phone.put("BM", "+1-441");
    country2phone.put("IO", "+246");
    country2phone.put("", "+357");
    country2phone.put("VG", "+1-284");
    country2phone.put("KY", "+1-345");
    country2phone.put("FK", "+500");
    country2phone.put("GI", "+350");
    country2phone.put("MS", "+1-664");
    country2phone.put("SH", "+290");
    country2phone.put("TC", "+1-649");
    country2phone.put("MP", "+1-670");
    country2phone.put("PR", "+1-787and1-939");
    country2phone.put("AS", "+1-684");
    country2phone.put("GU", "+1-671");
    country2phone.put("VI", "+1-340");
    country2phone.put("HK", "+852");
    country2phone.put("MO", "+853");
    country2phone.put("FO", "+298");
    country2phone.put("GL", "+299");
    country2phone.put("GF", "+594");
    country2phone.put("GP", "+590");
    country2phone.put("MQ", "+596");
    country2phone.put("RE", "+262");
    country2phone.put("AX", "+358-18");
    country2phone.put("AW", "+297");
    country2phone.put("AN", "+599");
    country2phone.put("SJ", "+47");
    country2phone.put("AC", "+247");
    country2phone.put("TA", "+290");
    country2phone.put("CS", "+381");
    country2phone.put("PS", "+970");
    country2phone.put("EH", "+212");
}
}

You could use the library called libphonenumber available on Github, made by Google developers. For example you can get the prefix using:

PhoneNumberUtil.getInstance().getCountryCodeForRegion("DE");

It also has a lot of useful functions to parse phone numbers.


Tidying up @oshai's answer

public class CountryToPhonePrefix {

private static Map<String, String> map = new HashMap<>();

public String prefixFor(String iso2CountryCode) {
    String result = map.get(iso2CountryCode);
    if (result == null) {
        throw new IllegalArgumentException("Unknown country code " + iso2CountryCode);
    }
    return result;
}

static {
    map.put("AC", "+247");
    map.put("AD", "+376");
    map.put("AE", "+971");
    map.put("AF", "+93");
    map.put("AG", "+1-268");
    map.put("AI", "+1-264");
    map.put("AL", "+355");
    map.put("AM", "+374");
    map.put("AN", "+599");
    map.put("AO", "+244");
    map.put("AR", "+54");
    map.put("AS", "+1-684");
    map.put("AT", "+43");
    map.put("AU", "+61");
    map.put("AW", "+297");
    map.put("AX", "+358-18");
    map.put("AZ", "+374-97");
    map.put("AZ", "+994");
    map.put("BA", "+387");
    map.put("BB", "+1-246");
    map.put("BD", "+880");
    map.put("BE", "+32");
    map.put("BF", "+226");
    map.put("BG", "+359");
    map.put("BH", "+973");
    map.put("BI", "+257");
    map.put("BJ", "+229");
    map.put("BM", "+1-441");
    map.put("BN", "+673");
    map.put("BO", "+591");
    map.put("BR", "+55");
    map.put("BS", "+1-242");
    map.put("BT", "+975");
    map.put("BW", "+267");
    map.put("BY", "+375");
    map.put("BZ", "+501");
    map.put("CA", "+1");
    map.put("CC", "+61");
    map.put("CD", "+243");
    map.put("CF", "+236");
    map.put("CG", "+242");
    map.put("CH", "+41");
    map.put("CI", "+225");
    map.put("CK", "+682");
    map.put("CL", "+56");
    map.put("CM", "+237");
    map.put("CN", "+86");
    map.put("CO", "+57");
    map.put("CR", "+506");
    map.put("CS", "+381");
    map.put("CU", "+53");
    map.put("CV", "+238");
    map.put("CX", "+61");
    map.put("CY", "+90-392");
    map.put("CY", "+357");
    map.put("CZ", "+420");
    map.put("DE", "+49");
    map.put("DJ", "+253");
    map.put("DK", "+45");
    map.put("DM", "+1-767");
    map.put("DO", "+1-809"); // and 1-829?
    map.put("DZ", "+213");
    map.put("EC", "+593");
    map.put("EE", "+372");
    map.put("EG", "+20");
    map.put("EH", "+212");
    map.put("ER", "+291");
    map.put("ES", "+34");
    map.put("ET", "+251");
    map.put("FI", "+358");
    map.put("FJ", "+679");
    map.put("FK", "+500");
    map.put("FM", "+691");
    map.put("FO", "+298");
    map.put("FR", "+33");
    map.put("GA", "+241");
    map.put("GB", "+44");
    map.put("GD", "+1-473");
    map.put("GE", "+995");
    map.put("GF", "+594");
    map.put("GG", "+44");
    map.put("GH", "+233");
    map.put("GI", "+350");
    map.put("GL", "+299");
    map.put("GM", "+220");
    map.put("GN", "+224");
    map.put("GP", "+590");
    map.put("GQ", "+240");
    map.put("GR", "+30");
    map.put("GT", "+502");
    map.put("GU", "+1-671");
    map.put("GW", "+245");
    map.put("GY", "+592");
    map.put("HK", "+852");
    map.put("HN", "+504");
    map.put("HR", "+385");
    map.put("HT", "+509");
    map.put("HU", "+36");
    map.put("ID", "+62");
    map.put("IE", "+353");
    map.put("IL", "+972");
    map.put("IM", "+44");
    map.put("IN", "+91");
    map.put("IO", "+246");
    map.put("IQ", "+964");
    map.put("IR", "+98");
    map.put("IS", "+354");
    map.put("IT", "+39");
    map.put("JE", "+44");
    map.put("JM", "+1-876");
    map.put("JO", "+962");
    map.put("JP", "+81");
    map.put("KE", "+254");
    map.put("KG", "+996");
    map.put("KH", "+855");
    map.put("KI", "+686");
    map.put("KM", "+269");
    map.put("KN", "+1-869");
    map.put("KP", "+850");
    map.put("KR", "+82");
    map.put("KW", "+965");
    map.put("KY", "+1-345");
    map.put("KZ", "+7");
    map.put("LA", "+856");
    map.put("LB", "+961");
    map.put("LC", "+1-758");
    map.put("LI", "+423");
    map.put("LK", "+94");
    map.put("LR", "+231");
    map.put("LS", "+266");
    map.put("LT", "+370");
    map.put("LU", "+352");
    map.put("LV", "+371");
    map.put("LY", "+218");
    map.put("MA", "+212");
    map.put("MC", "+377");
    map.put("MD", "+373-533");
    map.put("MD", "+373");
    map.put("ME", "+382");
    map.put("MG", "+261");
    map.put("MH", "+692");
    map.put("MK", "+389");
    map.put("ML", "+223");
    map.put("MM", "+95");
    map.put("MN", "+976");
    map.put("MO", "+853");
    map.put("MP", "+1-670");
    map.put("MQ", "+596");
    map.put("MR", "+222");
    map.put("MS", "+1-664");
    map.put("MT", "+356");
    map.put("MU", "+230");
    map.put("MV", "+960");
    map.put("MW", "+265");
    map.put("MX", "+52");
    map.put("MY", "+60");
    map.put("MZ", "+258");
    map.put("NA", "+264");
    map.put("NC", "+687");
    map.put("NE", "+227");
    map.put("NF", "+672");
    map.put("NG", "+234");
    map.put("NI", "+505");
    map.put("NL", "+31");
    map.put("NO", "+47");
    map.put("NP", "+977");
    map.put("NR", "+674");
    map.put("NU", "+683");
    map.put("NZ", "+64");
    map.put("OM", "+968");
    map.put("PA", "+507");
    map.put("PE", "+51");
    map.put("PF", "+689");
    map.put("PG", "+675");
    map.put("PH", "+63");
    map.put("PK", "+92");
    map.put("PL", "+48");
    map.put("PM", "+508");
    map.put("PR", "+1-787"); // and 1-939 ?
    map.put("PS", "+970");
    map.put("PT", "+351");
    map.put("PW", "+680");
    map.put("PY", "+595");
    map.put("QA", "+974");
    map.put("RE", "+262");
    map.put("RO", "+40");
    map.put("RS", "+381");
    map.put("RU", "+7");
    map.put("RW", "+250");
    map.put("SA", "+966");
    map.put("SB", "+677");
    map.put("SC", "+248");
    map.put("SD", "+249");
    map.put("SE", "+46");
    map.put("SG", "+65");
    map.put("SH", "+290");
    map.put("SI", "+386");
    map.put("SJ", "+47");
    map.put("SK", "+421");
    map.put("SL", "+232");
    map.put("SM", "+378");
    map.put("SN", "+221");
    map.put("SO", "+252");
    map.put("SO", "+252");
    map.put("SR", "+597");
    map.put("ST", "+239");
    map.put("SV", "+503");
    map.put("SY", "+963");
    map.put("SZ", "+268");
    map.put("TA", "+290");
    map.put("TC", "+1-649");
    map.put("TD", "+235");
    map.put("TG", "+228");
    map.put("TH", "+66");
    map.put("TJ", "+992");
    map.put("TK", "+690");
    map.put("TL", "+670");
    map.put("TM", "+993");
    map.put("TN", "+216");
    map.put("TO", "+676");
    map.put("TR", "+90");
    map.put("TT", "+1-868");
    map.put("TV", "+688");
    map.put("TW", "+886");
    map.put("TZ", "+255");
    map.put("UA", "+380");
    map.put("UG", "+256");
    map.put("US", "+1");
    map.put("UY", "+598");
    map.put("UZ", "+998");
    map.put("VA", "+379");
    map.put("VC", "+1-784");
    map.put("VE", "+58");
    map.put("VG", "+1-284");
    map.put("VI", "+1-340");
    map.put("VN", "+84");
    map.put("VU", "+678");
    map.put("WF", "+681");
    map.put("WS", "+685");
    map.put("YE", "+967");
    map.put("YT", "+262");
    map.put("ZA", "+27");
    map.put("ZM", "+260");
    map.put("ZW", "+263");
}}