[insaf021]

Dfp(DfpField, String) copies at most getRadixDigits() * 4 + 1 significant digits into its scratch buffer and stops reading the input once that buffer is full. If no decimal point has been seen by then, the decimal position is taken from the number of digits stored rather than the number of integer digits in the string, so every digit past the precision is lost from the exponent as well as the mantissa. With the default 20-digit field, newDfp("123456789012345678901234567890") returns 1.2345678901234568e20 instead of roughly 1.23e29, and "1234567890123456789012345678.5" gives the same e20 value because its decimal point sits past the cut-off and is never reached. The result is a finite, plausible-looking number that is off by a factor of ten per excess digit, with nothing beyond FLAG_INEXACT to signal it. It shows up when comparing toDouble() of long decimal strings against Double.parseDouble: the two agree up to 21 digits and then diverge sharply. When the buffer fills before a decimal point, the constructor now counts the remaining integer digits up to the point and uses that as the decimal position, so the value is still rounded at the precision limit but keeps its exponent; this is separate from the exponent handling changed in #341. The new test in DfpTest fails on master with x = 1.2345678901234568e20 and passes with the patch, and mvn verify on commons-math-core, commons-math-legacy-exception and commons-math-legacy-core is clean, as are the Dfp-using tests in commons-math-legacy.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 87.22%. Comparing base (f554608) to head (278814e).
⚠️ Report is 396 commits behind head on master.

Files with missing lines	Patch %	Lines
.../org/apache/commons/math4/legacy/core/dfp/Dfp.java	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #342      +/-   ##
============================================
+ Coverage     86.54%   87.22%   +0.67%     
+ Complexity     9787       91    -9696     
============================================
  Files           532      499      -33     
  Lines         35516    33533    -1983     
  Branches       6194     5853     -341     
============================================
- Hits          30738    29249    -1489     
+ Misses         3518     3164     -354     
+ Partials       1260     1120     -140     

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