Java从字符串创建枚举

我有枚举类

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;
    }
}

当我尝试创建枚举时：

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

Java向我抛出错误：

IllegalArgumentException occured : No enum constant models.PaymentType.subscr_signup

---

如何修复此问题？

valueOf

返回其标识符与您传入的字符串匹配的枚举项。
例如：

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，该方法循环通过

PaymentType.values（）

并返回匹配项。

枚举

类
.valueOf（）
方法将传递给它的字符串与enum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\u NEW”
，而不是
“subscr\u signup”

您需要编写一个静态方法，返回给定值的正确枚举实例。例如：

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);
}

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");
}

添加并使用此方法

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
}

枚举没有用于此操作的现成方法。您需要使用准确的字段名：

PaymentType.valueOf("SUBSCRIPTION_MODIFY");

或者编写自己的方法，例如：

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);
}

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：

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

印刷品：

SUBSCRIPTION_MODIFY

是枚举变量值，而不是枚举值。
因此，如果您想根据枚举的值名获取枚举，必须这样做：

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

我认为您必须在内部编写一个比较方法来创建额外的静态方法，该方法将搜索enum@wero这不是复制品。如果字符串不是相同的枚举值，则提供的示例不是解决方案。@ssh您阅读了提供的问题的第二个答案了吗？我不能使用它，因为我不能更改常量。您当然可以编写一个方法。为什么不呢？如果无法修改PaymentType枚举，只需使用
getType（）
访问器将其作为静态方法添加到其他地方，而不是直接使用
type
。