字符串与Java枚举的不区分大小写的匹配 [英] Case-insensitive matching of a string to a Java enum

问题描述

Java 为每个枚举< T>提供 valueOf（） code> object，所以给出一个枚举像

Java provides a valueOf() method for every Enum<T> object, so given an enum like

public enum Day {
  Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday
}

可以像

Day day = Day.valueOf("Monday");

如果字符串传递给 valueOf（）不匹配（区分大小写）现有的日值，抛出 IllegalArgumentException 。

If the string passed to valueOf() does not match (case sensitive) an existing Day value, an IllegalArgumentException is thrown.

要进行不区分大小写的匹配，可以在 Day 枚举中编写一个自定义方法，例如

To do a case-insensitive matching, one can write a custom method inside the Day enum, e.g.

public static Day lookup(String day) {
  for (Day d : Day.values()) {
    if (d.name().equalsIgnoreCase(day)) {
      return type;
    }
  }
  return null;
}

有没有任何通用的方式，不使用值缓存或任何其他额外的对象，写一个静态的 lookup（）方法，如上所述一次（即不是每个枚举），给定在编译时将 values（）方法隐式添加到 Enum< E> 类中？

Is there any generic way, without using caching of values or any other extra objects, to write a static lookup() method like the above only once (i.e., not for every enum), given that the values() method is implicitly added to the Enum<E> class at compile time?

这样一个通用 lookup（）方法的签名将类似于 Enum.valueOf （）方法，即：

The signature of such a "generic" lookup() method would be similar to the Enum.valueOf() method, i.e.:

public static <T extends Enum<T>> T lookup(Class<T> enumType, String name);

，它将完全实现 Day.lookup（）方法为任何枚举，而不需要为每个枚举重新编写相同的方法

and it would implement exactly the functionality of the Day.lookup() method for any enum, without the need to re-write the same method for each enum.

推荐答案

我发现特殊混合的泛型有点棘手，但这有用。

I found getting the special blend of generics a little tricky, but this works.

public static <T extends Enum<?>> T searchEnum(Class<T> enumeration,
        String search) {
    for (T each : enumeration.getEnumConstants()) {
        if (each.name().compareToIgnoreCase(search) == 0) {
            return each;
        }
    }
    return null;
}

示例

public enum Horse {
    THREE_LEG_JOE, GLUE_FACTORY
};

public static void main(String[] args) {
    System.out.println(searchEnum(Horse.class, "Three_Leg_Joe"));
    System.out.println(searchEnum(Day.class, "ThUrSdAy"));
}

这篇关于字符串与Java枚举的不区分大小写的匹配的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！