JavaSE选择结构——优化if-else的嵌套代码

// 请按你的实际需求修改参数
public String convertCountryName(String fullName) {
    if ("china".equalsIgnoreCase(fullName)) {
        return "CN";
    } else if ("america".equalsIgnoreCase(fullName)) {
        return "US";
    } else if ("japan".equalsIgnoreCase(fullName)) {
        return "JP";
    } else if ("england".equalsIgnoreCase(fullName)) {
        return "UK";
    } else if ("france".equalsIgnoreCase(fullName)) {
        return "FR";
    } else if ("germany".equalsIgnoreCase(fullName)) {
        return "DE";
    } else {
        throw new RuntimeException("unknown country");
    }
}

/**
 *
 */
public enum CountryEnum {
    china("CN"),
    america("US"),
    japan("JP"),
    england("UK"),
    france("FR"),
    germany("DE"),
    ;
    private String fullName;
    CountryEnum(String fullName) {
        this.fullName = fullName;
    }
    public String getFullName() {
        return fullName;
    }
}