How to compare two double values in Java

Question

A simple comparison of two double values in Java creates some problems  Let s consider the following simple code snippet in Java   package doublecomparision   final public class DoubleComparision        public static void main String   args                 double a   1 000001          double b   0 000001           System out println   n    a-b   1 0                The above code appears to return true  the evaluation of the expression   a-b   1 0  but it doesn t  It returns false instead because the evaluation of this expression is 0 9999999999999999 which was actually expected to be 1 0 which is not equal to 1 0 hence  the condition evaluates to boolean false  What is the best and suggested way to overcome such a situation

User · Answer

int mid   10          for  double j   2   mid  j  gt   0  j   j - 0 1                if  j    mid                    System out println  Never happens       is NOT printed                            if  Double compare j  mid     0                    System out println  No way        is NOT printed                            if  Math abs j - mid   lt  1e-6                    System out println  Ha        printed                                 System out println  Gotcha

User · Answer

double a   1 000001  double b   0 000001   System out println  a compareTo b       Returns    -1    a  is numerically less than  b   0    a  is equal to  b   1    a  is greater than  b

User · Answer

You can use Double compare  It compares the two specified double values

User · Answer

Instead of using doubles for decimal arithemetic  please use  java math BigDecimal  It would produce the expected results   For reference take a look at this stackoverflow question

User · Answer

Just use Double compare   method to compare double values  Double compare  d1 d2     0     double d1   0 0  double d2   0 0   System out println Double compare  d1 d2     0       true

User · Answer

Basically you shouldn t do exact comparisons  you should do something like this   double a   1 000001  double b   0 000001  double c   a-b  if  Math abs c-1 0   lt   0 000001

User · Answer

Consider this line of code   Math abs firstDouble - secondDouble   lt  Double MIN NORMAL   It returns whether firstDouble is equal to secondDouble  I m unsure as to whether or not this would work in your exact case  as Kevin pointed out  performing any math on floating points can lead to imprecise results  however I was having difficulties with comparing two double which were  indeed  equal  and yet using the  compareTo  method didn t return 0   I m just leaving this there in case anyone needs to compare to check if they are indeed equal  and not just similar

[java] How to compare two double values in Java?

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