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I want to assign 4294967295 to a variable (2^32-1) It is obvious that I can't do that with Integer, and can do it with Long.

However, I noted that Java 8 offers Unsigned Integers (at least some methods).

Does any one know what the method, Integer.parseUnsignedInt() does? When I input "4294967295" to that, and print the variable, it gives the output as -1 (-2 for 4294967294, -3 for 4294967293 and so on...)

Is there a way that I can still have 4294967295 in a variable?

Am I missing something here?

a=Integer.parseUnsignedInt("4294967295");
System.out.println(a);

This gives the output as -1 but I expected 4294967295.

Pubudu Dodangoda
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  • Show us your code that created the unsigned int – Bartlomiej Lewandowski Oct 15 '14 at 11:10
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    Don't think of it as a decimal number think of it as a series of bits, you are putting an unsigned number into a signed type, if you know what the bit representation of the number is then you know why you are getting -2 or whatever, then parse it as unsigned to get the decimal you expect – Neilos Oct 15 '14 at 11:17

3 Answers3

21

You can view that integer as unsigned int by calling toUnsignedString():

int uint = Integer.parseUnsignedInt("4294967295");
System.out.println(Integer.toUnsignedString(uint));

You can also call some other methods that interpret that int as unsigned.

For example :

long l = Integer.toUnsignedLong(uint);
System.out.println(l); // will print 4294967295

int x = Integer.parseUnsignedInt("4294967295");
int y = 5;
int cmp1 = Integer.compareUnsigned(x,y); // interprets x as 4294967295 (x>y) 
int cmp2 = Integer.compare(x,y); // interprets x as -1 (x<y)
Eran
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3

As far as I understand https://blogs.oracle.com/darcy/entry/unsigned_api, the unsigned support is not done by introducing a new type. The values are still stored in (signed) int variables but they provide methods to interpret the value as unsigned:

To avoid dealing with the overhead of boxed values and to allow reuse of the built-in arithmetic operators, the unsigned API support does not introduce new types like UnsignedInt with instance methods to perform addition, subtraction, etc. However, that lack of separate Java-level unsigned types does mean a programmer can accidentally improperly mix signed and unsigned values.

You used the "unsigned" version of parse, but you don't show which method you use to "print the variable". Probably you picked the (default) signed one.

chiccodoro
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0

Is there a way that I can still have 4294967295 in a varible?

Yes. Use long. (To me, it sounds like you're overthinking it.)

NPE
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