Today’s amusement in my job:
Rounding error from Double to BigDecimal, see java docs for public BigDecimal(double val).
Java creates a BigDecimal which is exactly equal to 0.1 (an unscaled value of 1, with a scale of 1), but it is actually equal to 0.1000000000000000055511151231257827021181583404541015625
Workaround 1: Convert Double to String before converting to BigDecimal, as suggested in the java docs for BigDecimal
BigDecimal b = new BigDecimal(Double.toString(double));
Workaround 2: Round!
Double d = ...; // your (rounded) value
BigDecimal b = new BigDecimal(d).setScale(2, BigDecimal.ROUND_HALF_UP);
.
Another problem with Double in Java: http://www.exploringbinary.com/java-hangs-when-converting-2-2250738585072012e-308/
electrobabe.at 
ein weiteres Problem mit Double in Java
http://www.exploringbinary.com/java-hangs-when-converting-2-2250738585072012e-308/
(danke cypher)
Round error ist kein error, sondern so dokumentiertes Verhalten:
“Translates a double into a BigDecimal which is the exact decimal representation of the double’s binary floating-point value.” (Javadoc)
Ps: Dein Tip zur JPA-Annotationen hat mir sehr geholfen. Danke
Es gibt einen netten Java-Puzzler zu genau dem Problem.
(kannst zu 7 Minuten vorspulen, aber der ganze Vortrag ist super)