How Do I Reimplement Valueof on Enumeration

Use Apache Commons Lang:

MyEnum myEnum = EnumUtils.getEnum(MyEnum.class, "MY_ENUM_VALUE");

Quote from the Javadoc for EnumUtils.getEnum:

Gets the enum for the class, returning null if not found.

This method differs from Enum.valueOf(java.lang.Class, java.lang.String) in that it does not throw an exception for an invalid enum name.

Is it absolutely necessary that the method is called valueOf like the method that enums have automatically? In the project that I'm currently working on we have similar methods, but we call them differently; for example, forName:

public static ESomeEnum forName(String name) {
    for (ESomeEnum e : ESomeEnum.values()) {
        if (e.name().equals(name)) {
            return e;
        }
    }

    return null;
}

You don't have to override valueOf. Here's what I did:

I had to "parse" some strings to enums and they didn't match with their declaration names, so I did a sort of reimplementation of valueOf(String name).

public enum Command {
    DIR("DIR"),
    PUT("PUT"),
    GET("GET"),
    OK("OK"),
    ERROR("ERROR"),
    READY("READY"),
    FIN("#FIN#");

    private String name;

    private Command(final String name) {
        this.name = name;
    }

    /**
     * Returns the desired Enum or throws an exception
     * @param commandName - String with the name contained by the Enum that you want
     * @return Command
     */
    public static Command getEnum(String commandName){
        // if the string is "#FIN#" returns Command.FIN.
        if(FIN.toString().equals(commandName)){
            return FIN;
        }
        // if the name matches any of the remaining enums return whichever one matches
        else if(Arrays.asList(Command.values()).contains(Command.valueOf(commandName))){
            return Command.valueOf(commandName);
        }
        // if it still wasn't found, throw an exception
        throw new IllegalArgumentException("No enum defined for this string: " + commandName);
    }

    @Override
    public String toString(){
            return name;
        }
    }

This code is tested and works.

You can use like:

Command k = Command.getEnum("#FIN#");
System.out.println(k.name() + "  " +k.toString());
k = Command.getEnum("PUT");
System.out.println(k.name() + "  " +k.toString());

And it's output would be:

FIN  #FIN#
PUT  PUT

Hope it helps.

You might consider creating a new (different name such as convert) static method in your enum classes.

public enum MyEnum{
      ....

     public static MyEnum convert(Object value){
       ...
     }
}