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public static PhoneProviderType getPhoneProvider(String phone) {
    // 截取前3或前4位電話號碼，判斷運營商
    String head_three = phone.substring(0, 3);
    PhoneProviderType phoneProviderType = pre_three.entrySet().stream().filter(e -> e.getValue().contains(head_three)).map(e -> e.getKey()).findFirst().orElse(null);
    if(phoneProviderType == null){
        String head_four = phone.substring(0, 4);
        phoneProviderType = pre_four.entrySet().stream().filter(e -> e.getValue().contains(head_four)).map(e -> e.getKey()).findFirst().orElse(null);
    }
    if(phoneProviderType == null){
        phoneProviderType = PhoneProviderType.聯通;
    }
    return phoneProviderType;
}