Re: ordinal() returns inconsistent values?
Lew wrote:
Todd wrote:
I have recently been told that the ordinal() method in a Java enum
will not necessarily return the same value in different
invocations of the JVM. Has anyone else found this?
Joshua Cranmer wrote:
To do so would contradict the API:
public final int ordinal()
Returns the ordinal of this enumeration constant (its position in
its enum declaration, where the initial constant is assigned an
ordinal of zero). Most programmers will have no use for this
method. It is designed for use by sophisticated enum-based data
structures, such as EnumSet and EnumMap.
Returns:
the ordinal of this enumeration constant
Todd wrote:
I fully agree. I was told that the JavaDocs were wrong. I tried
locating a source on the web to corroborate the assertion, but
couldn't find one.
"I was told ..."
Who told you? How authoritative is this source usually? What
evidence did they give for this outrageous assertion? Wouldn't it
break 'EnumSet' and 'EnumMap' if your source were correct?
To the last point, not necessarily, so long as it's consistent within a JVM
session and those classes are persisted in a way that doesn't assume it's
consistent across JVMs. Likewise, I think (though I could be wrong) that
1. Create a TreeMap
2. Serialize it to a file
3. Make code changes that change the ordering defined on its keys
4. Deserialize it
works.
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