precision - Java double addition rounding off -

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in java following expression results into

new double(1.0e22) + new double(3.0e22)  = 4.0e22

but

new double(1.0e22) + new double(4.0e22)  = 4.9999999999999996e22

i expecting 5.0e22. double limit 1.7976931348623157e308. appreciate help. machine's architecture x64 , jvm 64 bit.

welcome planet of floating point units. unfortunately, in real world, have give precision speed , breadth of representation. cannot avoid that: double approximate representation. actually, cannot represent number finite precision. still, it's approximation: less 0.00000000001% error. has nothing double upper limits, rather cpu limits, try doing more math python:

>>> 4.9999999999999996 / 5. 1.0 >>> 5. - 4.9999999999999996 0.0

see? side note, never check equality on double, use approximate equality:

if ((a - b) < epsilon)

where epsilon small value. java library has more appropriate, idea.

if insterested in theory, standard floating point operations ieee754


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