java从字符串中删除HashMap键

Question

我在数据库表列中有移动电话号码，格式为country_code，后跟mobile_number 所以手机号码格式是这样的

+91123456789 // country code of India is +91 followed by mobile number
+97188888888 // Country code of UAE +971

我有一个HashMap包含5个国家的国家代码

map.put("+91","India")
map.put("+94","Sri Lanka")
map.put("+881","Bangladesh")
map.put("+971","UAE")
map.put("+977","Nepal")

我的Bean结构是这样的

class UserDetails {

  // other fields
   String countryCode;
   String mobileNumber;
}

现在，我的任务是从数据库表列中获取移动电话号码，并将其分成两部分，然后设置countryCode和mobileNumber，但国家代码长度（在地图的键中）在3和4之间变化。这个检查可以通过使用subString()和equals()来完成，但我认为这不是正确的方法，那么解决这个问题的优雅（可能是在map key）方法是什么呢

Answer 1

虽然there is a library比seems to already do the trick好，但我想我会选择一个简单的自编解决方案：

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class CountryExtractor {
    private static final Map<String, String> COUNTRY_MAPPING = new HashMap<>();

    static {
        COUNTRY_MAPPING.put("+91", "India");
        COUNTRY_MAPPING.put("+94", "Sri Lanka");
        COUNTRY_MAPPING.put("+881", "Bangladesh");
        COUNTRY_MAPPING.put("+971", "UAE");
        COUNTRY_MAPPING.put("+977", "Nepal");
    }

    public static void main(String[] args) {
        String[] inputs = new String[] { "+91123456789", "+97188888888" };

        for (String input : inputs) {
            System.out.println(Arrays.toString(parseNumber(input)));
        }
    }

    private static String[] parseNumber(String number) {
        for (String countryCode : COUNTRY_MAPPING.keySet()) {
            if (number.startsWith(countryCode)) {
                return new String[] { countryCode, number.replace(countryCode, "") };
            }
        }
        return new String[0];
    }
}

输出：

[+91, 123456789]
[+971, 88888888]

请注意，当一个移动前缀是另一个前缀的子字符串时，这可能无法正常工作，但根据Wikipedia，国家呼叫代码是prefix codes，因此保证“系统中没有作为系统中任何其他码字前缀（初始段）的整个码字”

Answer 2

我觉得一张地图更好。一个例子

public static void main(String args[]) throws Exception {
    Map<String, String> map = new HashMap<>();
    put(map, "+91", "India");
    put(map, "+94", "Sri Lanka");
    put(map, "+881", "Bangladesh");
    put(map, "+971", "UAE");
    put(map, "+977", "Nepal");
    map = Collections.unmodifiableMap(map);

    String mobileNumber = "+91123456789";
    System.out.println(countryCode(map.keySet(), mobileNumber));
}

private static void put(Map<String, String> map, String key, String value) {
    if (countryCode(map.keySet(), key) != null) {
        throw new IllegalArgumentException("...");
    }
    map.put(key, value);
}

public static String countryCode(Set<String> countryCodes, String number) {
    if (number == null || number.length() < 3) {
        throw new IllegalArgumentException("...");
    }
    String code = number.substring(0, 3);
    if (!countryCodes.contains(code)) {
        if (number.length() > 3) {
            code = number.substring(0, 4);
            if (!countryCodes.contains(code)) {
                code = null;
            }
        } else {
            code = null;
        }
    }
    return code;
}

Answer 3

你可以用两张地图来显示不同长度的国家代码，然后先搜索3个字母的匹配项，然后再搜索4个字母的匹配项

    HashMap<String, String > threeLetterCodes = new HashMap<String, String>();
    threeLetterCodes.put("+91","India");
    threeLetterCodes.put("+94","Sri Lanka");


    HashMap<String, String > fourLetterCodes = new HashMap<String, String>();        
    fourLetterCodes.put("+881","Bangladesh");
    fourLetterCodes.put("+971","UAE");
    fourLetterCodes.put("+977","Nepal");

    String test = "+97188888888";

    String prefix = test.substring(0, 3);
    String country = threeLetterCodes.get(prefix);
    if (country == null) {
        prefix = test.substring(0, 4);
        country = fourLetterCodes.get(prefix);
    }

    System.out.println(country);

输出：

UAE