BigDecimal pitfalls

Examples of errors:

Why RoundingMode?

Because 10/3 => ArithmeticException

• ptifall: new BigDecimal("10").divide(new BigDecimal("3"))
• => ArithmeticException (result is 3.3333.....333)
• solution [use RoundingMode]: new BigDecimal("10").divide(new BigDecimal("3"), RoundingMode.HALF_UP)
  
• => OK

Why Precision?

Because 3/1000 == 0

• ptifall: new BigDecimal("3").divide(new BigDecimal("10000"), RoundingMode.HALF_UP)
  
• => 0.0003 => 0
• solution [use Precision (Presision+RoundingMode = MathContext)]: 
• int precision = 10;
  
• public static MathContext MATH_CONTEXT = new MathContext(precision, RoundingMode.HALF_UP);
• new BigDecimal("3").divide(new BigDecimal("10000"), MATH_CONTEXT) 

Therefore when deviding BigDecimals always use MathContext (i.e. RoundingMode and Precision).