从字符串创建Java枚举


Java create enum from String

本问题已经有最佳答案，请猛点这里访问。

我有枚举类

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public enum PaymentType {

    /**
     * This notify type we receive when user make first subscription payment.
     */
    SUBSCRIPTION_NEW("subscr_signup"),

    /**
     * This notify type we receive when user make subscription payment for next
     * month.
     */
    SUBSCRIPTION_PAYMENT("subscr_payment"),

    /**
     * This notify type we receive when user cancel subscription from his paypal
     * personal account.
     */
    SUBSCRIPTION_CANCEL("subscr_cancel"),

    /**
     * In this case the user cannot change the amount or length of the
     * subscription, they can however change the funding source or address
     * associated with their account. Those actions will generate the
     * subscr_modify IPN that we are receiving.
     */
    SUBSCRIPTION_MODIFY("subscr_modify"),

    /**
     * Means that the subscription has expired, either because the subscriber
     * cancelled it or it has a fixed term (implying a fixed number of payments)
     * and it has now expired with no further payments being due. It is sent at
     * the end of the term, instead of any payment that would otherwise have
     * been due on that date.
     */
    SUBSCRIPTION_EXPIRED("subscr_eot"),

    /** User have no money on card, CVV error, another negative errors. */
    SUBSCRIPTION_FAILED("subscr_failed");

    private String type;

    PaymentType(String type) {
        this.type = type;
    }

    String getType() {
        return type;
    }
}

尝试创建枚举时：

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PaymentType type = PaymentType.valueOf("subscr_signup");

Java向我抛出错误：

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IllegalArgumentException occured : No enum constant models.PaymentType.subscr_signup

我怎么能解决这个问题？

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添加并使用此方法

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public static PaymentType parse(String type) {
    for (PaymentType paymentType : PaymentType.values()) {
        if (paymentType.getType().equals(type)) {
            return paymentType;
        }
    }
    return null; //or you can throw exception
}
相关讨论

枚举尚未准备好对此使用方法。您要么需要使用准确的字段名：

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PaymentType.valueOf("SUBSCRIPTION_MODIFY");

或者编写自己的方法，例如：

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public static PaymentType fromString(String string) {
  for (PaymentType pt : values()) {
    if (pt.getType().equals(string)) {
      return pt;
    }
  }
  throw new NoSuchElementException("Element with string" + string +" has not been found");
}

所以这个代码：

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public static void main(String[] args) {
  System.out.println(PaymentType.fromString("subscr_modify"));
}

印刷品：

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SUBSCRIPTION_MODIFY

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subscr_signup

是枚举变量值，而不是枚举值。因此，如果要根据枚举的值名称获取枚举，则必须这样做：

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PaymentType type = PaymentType.valueOf("SUBSCRIPTION_NEW");

Enum类.valueOf()方法将传递给它的字符串与枚举实例的name属性(实例名称的实际值)进行比较，因此在您的示例中，这将是"SUBSCRIPTION_NEW"而不是"subscr_signup"。

您需要编写一个静态方法，该方法为给定值返回正确的枚举实例。例如：

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public static PaymentType byTypeString(String type) {
    for (PaymentType instance : values()) {
        if (instance.type.equals(type)) {
            return instance;
        }
    }
    throw new IllegalArgumentException("No PaymentType enum instance for type:" + type);
}
相关讨论

valueOf返回其标识符与您传入的字符串匹配的枚举项。例如：

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PaymentType t = PaymentType.valueOf("SUBSCRIPTION_NEW");

如果要获取其type字段与给定字符串匹配的枚举项，请在PaymentType上编写一个静态方法，该方法通过PaymentType.values()循环并返回匹配项。

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