CODEWITHSUNDEEP
javafloating-pointdata-conversionunsigned-integer
Johannes Kuhn
Johannes Kuhn

Reputation: 15163

Convert double to unsigned integer in Java

I'm trying to convert a double into an unsigned int in Java.

With unsigned int I mean the range from 0 to 4294967295.
I use int as carrier - and it can be converted to a String with Integer.toUnsignedString.

I don't care what result I get if

As long as I get any result.

A simple cast does not work:

(int) 4294967295d == 2147483647
(int) 2147483648d == 2147483647

So the problematic range is 2147483648d - 4294967295d.

Is there a fast way to cover that range correctly?

tl;dr: In C I would use (unsigned int) dblValue - what would I use in Java for that?

Upvotes: 0

Views: 992

Answers (1)

rzwitserloot
rzwitserloot

Reputation: 103018

4294967295f

That's not a thing. That float does not exist. It gets rounded. Don't use floats, there's almost no point to them. It works as a double.

Is there a fast way to cover that range correctly?

Once you realize that your question makes no sense and move to doubles instead, yeah. Cast to long, cast to int:

double d = 4294967295.0;
int i = (int) (long) d;
System.out.println(i);
System.out.println(Integer.toUnsignedString(i));
> -1
> 4294967295

Upvotes: 6

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