How to test if a double is zero

Question

I have some code like this   class Foo       public double x     void test         Foo foo   new Foo            Is this a valid way to test for zero   x  hasn t been set to anything yet      if  foo x    0                foo x   0 0          Will the same test be valid      if  foo x    0               I basically want to avoid a divide-by-zero exception in the future   Thanks

User · Answer

In Java  0 is the same as 0 0  and doubles default to 0  though many advise always setting them explicitly for improved readability   I have checked and foo x    0 and foo x    0 0 are both true if foo x is zero

User · Answer

Yes  it s a valid test although there s an implicit conversion from int to double  For clarity simplicity you should use  foo x    0 0  to test  That will hinder NAN errors division by zero  but the double value can in some cases be very very very close to 0  but not exactly zero  and then the test will fail  I m talking about in general now  not your code   Division by that will give huge numbers   If this has anything to do with money  do not use float or double  instead use BigDecimal

User · Answer

Yes  all primitive numeric types default to 0   However  calculations involving floating-point types  double and float  can be imprecise  so it s usually better to check whether it s close to 0   if  Math abs foo x   lt  2   Double MIN VALUE    You need to pick a margin of error  which is not simple

User · Answer

The safest way would be bitwise OR ing your double with 0  Look at this XORing two doubles in Java   Basically you should do if   Double doubleToRawLongBits foo x    0      if it is really 0

User · Answer

Numeric primitives in class scope are initialized to zero when not explicitly initialized   Numeric primitives in local scope  variables in methods  must be explicitly initialized   If you are only worried about division by zero exceptions  checking that your double is not exactly zero works great   if value    0        divide by value is safe when value is not exactly zero    Otherwise when checking if a floating point value like double or float is 0  an error threshold is used to detect if the value is near 0  but not quite 0   public boolean isZero double value  double threshold       return value  gt   -threshold  amp  amp  value  lt   threshold

[java] How to test if a double is zero?

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