Re: Using enums to avoid using switch/if

Lew <>
Tue, 23 Mar 2010 07:15:37 -0700 (PDT)
Lew quoted or indirectly quoted someone who said :

I need a mechanism to map string to enum.

Why do you not attribute the quote to the one who actually wrote it?

Roedy Green wrote:

see the built-in valueOf function. I often override it to make it
case insensitive and allow aliases.

I doubt that very much. Static methods cannot be overridden.

While there is some value in hiding the 'valueOf' method, I prefer to
use a differently-named method for the same purpose. I am loathe to
(apparently) change the behavior of such a standard, language-defined
method as 'Enum.valueOf'. Instead I use a static 'fromString()'
method to be the companion for 'toString'.

The 'Enum' Javadocs suggest that '[a]n enum type should override
[toString] when a more "programmer-friendly" string form exists.' I
find it mnemonic and symmetrical to go from "programmer-friendly"
string form to enum constant with 'fromString'. This also preserves
the semantics of 'valueOf' as documented in the JLS. Furthermore, I
use 'valueOf' as the fallback if 'fromString' is otherwise unable to
locate the enum constant.

My enum template is:

/* ${name}.java
package ${package};

 * ${name}.
public enum ${name}

    private final String repr; // "friendly" representation
     * Constructor.
     * @param rep String representation of enum value.
    ${name}( String rep )
        this.repr = rep;

    public final String toString()
        return this.repr;

     * Look up enum constant from String representation.
     * @param rep String representation of enum value.
     * @return ${name} constant matching the representation.
    public static ${name} fromString( final String rep )
        if ( rep == null )
            return null;
        for ( ${name} val : values() )
            if ( rep.equals( val.toString() ) )
                return val;
        return valueOf( rep );


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