CODEWITHSUNDEEP
javafloating-point-precision
user1508893
user1508893

Reputation: 9783

float vs double (in Java)

Is there ever a case where these two methods would return different values given the same inputs?

int compare1(float a, float b)
{
    return Double.compare(a, b);
}

int compare2(float a, float b)
{
    return Float.compare(a, b);
}

By the same token, is it true (or false) that any number storable in a java's Float can be stored in a java's Double without losing any precision?

Thanks

Upvotes: 5

Views: 1181

Answers (3)

NPE
NPE

Reputation: 500157

Every float can be represented exactly as a double. From this it follows that the two functions always return the same result.

Upvotes: 4

SLaks
SLaks

Reputation: 887195

Yes; casting doubles to floats can yield different results.

If the difference between a and b is too small to show up in a float, compare2() will return 0 whereas compare1() would not.

You just edited the question to reverse what you were asking. The new answer is:

I'm almost certain that they will always be the same.

Upvotes: 8

Eduardo
Eduardo

Reputation: 8392

A double just gives you more bits of precision beyond the decimal place than the float. If all those those extra bits are zero then you have the same value as the float. So yes, all floats can be converted to doubles without losing precision.

Upvotes: 1

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