Tutorials:
1. http://www.javaworld.com/article/2075315/core-java/make-cents-with-bigdecimal.html
2. https://topic.alibabacloud.com/a/how-to-use-java-bigdecimala-tutorial__java_1_27_20230422.html
Discussions:
Double vs BigDecimal: http://stackoverflow.com/questions/3413448/double-vs-bigdecimal
Most important:
1. BigDecimals are immutable.
