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TIOBE - Java Coding Standard

Rule:  Basic23Checked automatically with code checker

Synopsis:Avoid creating BigDecimal with a decimal (float/double) literal. Use a String literal
Severity Level:1

One might assume that "new BigDecimal(.1)" is exactly equal to .1, but it is actually equal to .1000000000000000055511151231257827021181583404541015625. This is so because .1 cannot be represented exactly as a double (or, for that matter, as a binary fraction of any finite length). Thus, the long value that is being passed in to the constructor is not exactly equal to .1, appearances notwithstanding. The (String) constructor, on the other hand, is perfectly predictable: 'new BigDecimal(".1")' is exactly equal to .1, as one would expect. Therefore, it is generally recommended that the (String) constructor be used in preference to this one.
import java.math.BigDecimal;
public class Test {

    public static void main(String[] args) {
      // this would trigger the rule
     BigDecimal bd=new BigDecimal(1.123);
      // this wouldn't trigger the rule
     BigDecimal bd=new BigDecimal("1.123");
      // this wouldn't trigger the rule
     BigDecimal bd=new BigDecimal(12);