Java's BigDecimal.

Where to use Java's BigDecimal?
A example where it can be used is in applications which needs floating points with built in rounding facility.

Consider a case, where money is stored as a decimal in database. Sql mapping link states: "The recommended Java mapping for the DECIMAL and NUMERIC types is java.math.BigDecimal. The java.math.BigDecimal type provides math operations to allow BigDecimal types to be added, subtracted, multiplied, and divided with other BigDecimal types, with integer types, and with floating point types."

Lets say we want to compute a currency of another country. With currency conversion rate, a currency can be converted into required one. Using BigDecimal's divide method one can achieve it by mentioning the scale factor and rounding strategy.

2 is the scale (decides the number of digits after decimal point) and ROUND_HALF_EVEN strategy is banker's rounding.

BigDecimal amount = new BigDecimal(1);
BigDecimal rate = new BigDecimal(3);
BigDecimal destinationAmount = amount.divide(rate, 2, BigDecimal.ROUND_HALF_EVEN);