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From "Mark A. Ziesemer (JIRA)" <j...@apache.org>
Subject [jira] [Created] (LANG-882) LookupTranslator accepts CharSequence as input, but fails to work with implementations other than String
Date Thu, 28 Mar 2013 16:27:15 GMT
Mark A. Ziesemer created LANG-882:
-------------------------------------

             Summary: LookupTranslator accepts CharSequence as input, but fails to work with
implementations other than String
                 Key: LANG-882
                 URL: https://issues.apache.org/jira/browse/LANG-882
             Project: Commons Lang
          Issue Type: Bug
          Components: lang.text.translate.*
    Affects Versions: 3.1
            Reporter: Mark A. Ziesemer


The core of {{org.apache.commons.lang3.text.translate}} is a {{HashMap<CharSequence, CharSequence>
lookupMap}}.

>From the Javadoc of {{CharSequence}} (emphasis mine):
{quote}
This interface does not refine the general contracts of the equals and hashCode methods. The
result of comparing two objects that implement CharSequence is therefore, in general, undefined.
Each object may be implemented by a different class, and there is no guarantee that each class
will be capable of testing its instances for equality with those of the other. *It is therefore
inappropriate to use arbitrary CharSequence instances as elements in a set or as keys in a
map.*
{quote}

The current implementation causes code such as the following to not work as expected:

{code}
CharSequence cs1 = "1 < 2";
CharSequence cs2 = CharBuffer.wrap("1 < 2".toCharArray());

System.out.println(StringEscapeUtils.ESCAPE_HTML4.translate(cs1));
System.out.println(StringEscapeUtils.ESCAPE_HTML4.translate(cs2));
{code}

... which gives the following results (but should be identical):
{noformat}
1 &lt; 2
1 < 2
{noformat}

The problem, at a minimum, is that {{CharBuffer.equals}} is even documented in the Javadoc
that:
{quote}
A char buffer is not equal to any other type of object.
{quote}

... so a lookup on a CharBuffer in the Map will always fail when compared against the String
implementations that it contains.

An obvious work-around is to instead use something along the lines of either of the following:
{code}
System.out.println(StringEscapeUtils.ESCAPE_HTML4.translate(cs2.toString()));
System.out.println(StringEscapeUtils.escapeHtml4(cs2.toString()));
{code}

... which forces everything back to a {{String}}.  However, this is not practical when working
with large sets of data, which would require significant heap allocations and garbage collection
concerns.  (As such, I was actually trying to use the {{translate}} method that outputs to
a {{Writer}} - but simplified the above examples to omit this.)

Another option that I'm considering is to use a custom {{CharSequence}} wrapper around a {{char[]}}
that implements {{hashCode()}} and {{equals()}} to work with those implemented on {{String}}.
 (However, this will be interesting due to the symmetric assumption - which is further interesting
that {{String.equals}} is currently implemented using {{instanceof}} - even though {{String}}
is {{final}}...)

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