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http://issues.apache.org/bugzilla/show_bug.cgi?id=29294 [lang][PATCH] lang.math.Fraction class deficiencies Summary: [lang][PATCH] lang.math.Fraction class deficiencies Product: Commons Version: 2.0 Final Platform: PC OS/Version: Linux Status: NEW Severity: Enhancement Priority: Other Component: Lang AssignedTo: [EMAIL PROTECTED] ReportedBy: [EMAIL PROTECTED] The attached patch addresses several deficiencies in the Fraction class: a) 'reduction' should never be necessary. The fraction is stored as a pair of relatively prime integers (i.e. always in simplified form). The reduce() and getReducedFraction() methods have been deprecated and are now a no-op, and identical to getFraction(), respectively. The static field TWO_QUARTERS is also deprecated; it is now identical to the field ONE_HALF. b) this also fixes the API oddity where currently a.compareTo(b)==0 does not imply that a.equals(b). Once fractions are simplified, equals() corresponds correctly to numerical equality. c) the hashCode() method currently has a race condition if used in multithreaded code: two threads accessing a hashcode which has not yet been hashed may obtain different values returned from hashCode(). d) the gcd algorithm used in fraction has been changed to use a more efficient 'binary' algorithm which does not require division. e) all code has been reviewed so that values at the edges of the range of integers (ie Integer.MIN_VALUE and Integer.MAX_VALUE) are handled correctly. Note that Integer.MIN_VALUE cannot be negated, so this entails typically maintaining values as negative numbers when magnitudes are required. [See for example the patch to Fraction.toProperString()] f) the current pow() algorithm suffers from numerical inaccuracies due to casting between double and int. It has been replaced by a double-and-multiply method which guarantees accuracy. The new pow algorithm supports negative powers as well (up to an including Integer.MIN_VALUE) g) A 'resolveObject' method has been added to maintain backwards-compatibility with existing serialized Fractions. These are now simplified on deserialization. h) The addition and multiplication algorithms used have been updated to conform to those described in Knuth's "The Art of Computer Programming" section 4.5. This also means they will operate with larger fractions before overflowing. i) All overflow conditions ought to throw an ArithmeticException. This was not the case in the existing code (some overflows silently corrupted the result). j) The JUnit tests for this class have been extended to test and verify all of the above. Clover now indicates very few uncovered lines of code, most of which are legitimately unreachable. Checkstyle emits no warnings. The javadoc for all methods has been extended and corrected. --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
