[java] Check if enum exists in Java

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"));
    }
}

Examples related to java

Under what circumstances can I call findViewById with an Options Menu / Action Bar item? How much should a function trust another function How to implement a simple scenario the OO way Two constructors How do I get some variable from another class in Java? this in equals method How to split a string in two and store it in a field How to do perspective fixing? String index out of range: 4 My eclipse won't open, i download the bundle pack it keeps saying error log

Examples related to string

How to split a string in two and store it in a field String method cannot be found in a main class method Kotlin - How to correctly concatenate a String Replacing a character from a certain index Remove quotes from String in Python Detect whether a Python string is a number or a letter How does String substring work in Swift How does String.Index work in Swift swift 3.0 Data to String? How to parse JSON string in Typescript

Examples related to enums

Enums in Javascript with ES6 Check if value exists in enum in TypeScript Why Python 3.6.1 throws AttributeError: module 'enum' has no attribute 'IntFlag'? TypeScript enum to object array How can I loop through enum values for display in radio buttons? How to get all values from python enum class? Get enum values as List of String in Java 8 enum to string in modern C++11 / C++14 / C++17 and future C++20 Implementing Singleton with an Enum (in Java) Swift: Convert enum value to String?

Examples related to compare

Checking for duplicate strings in JavaScript array How to compare two files in Notepad++ v6.6.8 How to compare LocalDate instances Java 8 Comparing the contents of two files in Sublime Text comparing elements of the same array in java How to compare two dates along with time in java bash string compare to multiple correct values Query comparing dates in SQL How to compare two java objects Comparing two integer arrays in Java