I'm trying to convert long 1099 to BigDecimal 10.99; This gives me 11.00:
long cost = 1099;
MathContext CENTS = new MathContext(2,RoundingMode.HALF_EVEN);
BigDecimal result = (new BigDecimal(cost,CENTS)).movePointLeft(2);
AFAIK this should work. What's my bonehead error?
The error is that there's a distinction between scale and precision. The constructor of MathContext accepts a precision, which is a total number of decimal digits on either side of the decimal point. (For example, the original BigDecimal you had was essentially 11 * 10^2, as if it were in scientific notation.)
Change it to new MathContext(4, RoundingMode.HALF_EVEN).
new BigDecimal( 1099L )
.movePointLeft(2)
Use constructor taking only a long, without the MathContext.
See this code run live at IdeOne.com.
Use the BigDecimal.valueOf(long unscaledVal, int scale) method:
long cost = 1099;
BigDecimal result = BigDecimal.valueOf(cost, 2);
System.out.println(result); // 10.99