BigDecimal equals versus compareTo

Question

Consider the simple test class   import java math BigDecimal           author The Elite Gentleman        public class Main                    param args             public static void main String   args               TODO Auto-generated method stub         BigDecimal x   new BigDecimal  1            BigDecimal y   new BigDecimal  1 00            System out println x equals y            System out println x compareTo y     0    true    false               You can  consciously  say that x is equal to y  not object reference   but when you run the program  the following result shows   false true   Question  What s the difference between compareTo   and equals   in BigDecimal that compareTo can determine that x is equal to y   PS  I see that BigDecimal has an inflate   method on equals   method  What does inflate   do actually

User · Answer

I see that BigDecimal has an inflate   method on equals   method  What does inflate   do actually    Basically  inflate   calls BigInteger valueOf intCompact  if necessary  i e  it creates the unscaled value that is stored as a BigInteger from long intCompact  If you don t need that BigInteger and the unscaled value fits into a long BigDecimal seems to try to save space as long as possible

User · Answer

I believe that the correct answer would be to make the two numbers  BigDecimals   have the same scale  then we can decide about their equality  For example  are these two numbers equal   1 00001 and 1 00002   Well  it depends on the scale  On the scale 5  5 decimal points   no they are not the same  but on smaller decimal precisions  scale 4 and lower  they are considered equal  So I suggest make the scale of the two numbers equal and then compare them

User · Answer

You can also compare with double value  BigDecimal a  new BigDecimal  1 1    BigDecimal b  new BigDecimal  1 1    System out println a doubleValue    b doubleValue

User · Answer

The answer is in the JavaDoc of the equals   method      Unlike compareTo  this method considers two BigDecimal objects equal only if they are equal in value and scale  thus 2 0 is not equal to 2 00 when compared by this method     In other words  equals   checks if the BigDecimal objects are exactly the same in every aspect  compareTo    only  compares their numeric value   As to why equals   behaves this way  this has been answered in this SO question

[java] BigDecimal equals() versus compareTo()

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