Get enum value from string constructor

Question

In Java, I am trying to get the enum value from a string.

For example I got:

MESSENGERINIT("@L")

This is in the enum as well:

private String header;

private ServerPackets(String header) 
{
    this.header = header;
}

public String getHeader()
{
    return this.header;
    //more code here.
}

But if I try to use:

System.out.println("[" + ServerPackets.valueOf(header) + 
    "] - Received unregistered header " + 
    Base64Encoding.decode(header) + "(" + header + ") with body " + 
    connection.reader.toString());

I get this error:

java.lang.IllegalArgumentException: No enum constant 
com.kultakala.communication.ServerPackets.@L
    at java.lang.Enum.valueOf(Unknown Source)</code>

What does the error message mean and what I'm doing wrong?

Andy Thomas · Accepted Answer · 2013-04-02 14:41:03Z

7

Enum.valueof(String) uses the name of the enumerator -- MESSENGERINIT -- not the string you passed to the constructor.

If you want to map other strings to the enumerators, consider creating a static map in the enumerator class.

For example:

enum ServerPackets {
...

private static Map<String,ServerPackets> s_map = new HashMap<String,ServerPackets>();
static {
    map.put( "@L", MESSENGERINIT);
    ...
}
public ServerPackets getEnumFromHeader( String header ) {
   return map.get( header );
}

edited Apr 2, 2013 at 14:41

answered Apr 2, 2013 at 14:27

Andy Thomas

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4 Comments

Joshua Bakker Over a year ago

Is there a way to get the name of the enum value by the string of the constructor?

Axel Over a year ago

+1 You could create a static fromString(String s) method that iterates over ServerPackets.values() and returns the matching enum (if found).

OldCurmudgeon Over a year ago

Don't forget the enum.valueOf(String) method.

Andy Thomas Over a year ago

JoshuaBakker - See edit above. Axel's linear approach may also be appropriate. @OldCurmudgeon - that's being used in the question.

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