Check if enum exists in Java

Question

Is there anyway to check if an enum exists by comparing it to a given string? I can't seem to find any such function. I could just try to use the valueOf method and catch an exception but I'v been taught that catching runtime exceptions is not good practice. Anybody have any ideas?

Answer 1

If I need to do this, I sometimes build a Set<String> of the names, or even my own Map<String,MyEnum> - then you can just check that.

A couple of points worth noting:

• Populate any such static collection in a static initializer. Don't use a variable initializer and then rely on it having been executed when the enum constructor runs - it won't have been! (The enum constructors are the first things to be executed, before the static initializer.)
• Try to avoid using values() frequently - it has to create and populate a new array each time. To iterate over all elements, use EnumSet.allOf which is much more efficient for enums without a large number of elements.

Sample code:

import java.util.*;  enum SampleEnum {     Foo,     Bar;      private static final Map<String, SampleEnum> nameToValueMap =         new HashMap<String, SampleEnum>();          static {         for (SampleEnum value : EnumSet.allOf(SampleEnum.class)) {             nameToValueMap.put(value.name(), value);         }     }          public static SampleEnum forName(String name) {         return nameToValueMap.get(name);     } }  public class Test {     public static void main(String [] args)         throws Exception { // Just for simplicity!         System.out.println(SampleEnum.forName("Foo"));         System.out.println(SampleEnum.forName("Bar"));         System.out.println(SampleEnum.forName("Baz"));     } } 

Of course, if you only have a few names this is probably overkill - an O(n) solution often wins over an O(1) solution when n is small enough. Here's another approach:

import java.util.*;  enum SampleEnum {     Foo,     Bar;      // We know we'll never mutate this, so we can keep     // a local copy.     private static final SampleEnum[] copyOfValues = values();          public static SampleEnum forName(String name) {         for (SampleEnum value : copyOfValues) {             if (value.name().equals(name)) {                 return value;             }         }         return null;     } }  public class Test {     public static void main(String [] args)         throws Exception { // Just for simplicity!         System.out.println(SampleEnum.forName("Foo"));         System.out.println(SampleEnum.forName("Bar"));         System.out.println(SampleEnum.forName("Baz"));     } }