Declaring an unsigned int in Java

Question

Is there a way to declare an unsigned int in Java   Or the question may be framed as this as well  What is the Java equivalent of unsigned   Just to tell you the context I was looking at Java s implementation of String hashcode    I wanted to test the possibility of collision if the integer were 32 unsigned int

User · Answer

For unsigned numbers you can use these classes from Guava library:

They support various operations:

plus
minus
times
mod
dividedBy

The thing that seems missing at the moment are byte shift operators. If you need those you can use BigInteger from Java.

User · Answer

Whether a value in an int is signed or unsigned depends on how the bits are interpreted - Java interprets bits as a signed value  it doesn t have unsigned primitives   If you have an int that you want to interpret as an unsigned value  e g  you read an int from a DataInputStream that you know should be interpreted as an unsigned value  then you can do the following trick  int fourBytesIJustRead   someObject getInt    long unsignedValue   fourBytesIJustRead  amp  0xffffffffL   Note  that it is important that the hex literal is a long literal  not an int literal - hence the  L  at the end

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It seems that you can handle the signing problem by doing a  logical AND  on the values before you use them   Example  Value of byte   header 0  is 0x86     System out println  Integer    int header 0          int header 0  amp 0xff      Result   Integer -122   134

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Java does not have a datatype for unsigned integers   You can define a long instead of an int if you need to store large values   You can also use a signed integer as if it were unsigned  The benefit of two s complement representation is that most operations  such as addition  subtraction  multiplication  and left shift  are identical on a binary level for signed and unsigned integers  A few operations  division  right shift  comparison  and casting   however  are different  As of Java SE 8  new methods in the Integer class allow you to fully use the int data type to perform unsigned arithmetic      In Java SE 8 and later  you can use the int data type to represent an unsigned 32-bit integer  which has a minimum value of 0 and a maximum value of 2 32-1  Use the Integer class to use int data type as an unsigned integer  Static methods like compareUnsigned  divideUnsigned etc have been added to the Integer class to support the arithmetic operations for unsigned integers    Note that int variables are still signed when declared but unsigned arithmetic is now possible by using those methods in the Integer class

User · Answer

Use char for 16 bit unsigned integers

User · Answer

There are good answers here  but I don   t see any demonstrations of bitwise operations  Like Visser  the currently accepted answer  says  Java signs integers by default  Java 8 has unsigned integers  but I have never used them   Without further ado  let   s do it    RFC 868 Example What happens if you need to write an unsigned integer to IO  Practical example is when you want to output the time according to RFC 868  This requires a 32-bit  big-endian  unsigned integer that encodes the number of seconds since 12 00 A M  January 1  1900  How would you encode this  Make your own unsigned 32-bit integer like this  Declare a byte array of 4 bytes  32 bits  Byte my32BitUnsignedInteger     new Byte 4     represents the time  s   This initializes the array  see Are byte arrays initialised to zero in Java   Now you have to fill each byte in the array with information in the big-endian order  or little-endian if you want to wreck havoc   Assuming you have a long containing the time  long integers are 64 bits long in Java  called secondsSince1900  Which only utilizes the first 32 bits worth  and you   ve handled the fact that Date references 12 00 A M  January 1  1970   then you can use the logical AND to extract bits from it and shift those bits into positions  digits  that will not be ignored when coersed into a Byte  and in big-endian order  my32BitUnsignedInteger 0     byte    secondsSince1900  amp  0x00000000FF000000L   gt  gt  24      first byte of array contains highest significant bits  then shift these extracted FF bits to first two positions in preparation for coersion to Byte  which only adopts the first 8 bits  my32BitUnsignedInteger 1     byte    secondsSince1900  amp  0x0000000000FF0000L   gt  gt  16   my32BitUnsignedInteger 2     byte    secondsSince1900  amp  0x000000000000FF00L   gt  gt  8   my32BitUnsignedInteger 3     byte    secondsSince1900  amp  0x00000000000000FFL      no shift needed  Our my32BitUnsignedInteger is now equivalent to an unsigned 32-bit  big-endian integer that adheres to the RCF 868 standard  Yes  the long datatype is signed  but we ignored that fact  because we assumed that the secondsSince1900 only used the lower 32 bits   Because of coersing the long into a byte  all bits higher than 2 7  first two digits in hex  will be ignored  Source referenced  Java Network Programming  4th Edition

User · Answer

Perhaps this is what you meant   long getUnsigned int signed        return signed  gt   0   signed   2    long  Integer MAX VALUE   2   signed       getUnsigned 0    0 getUnsigned 1    1 getUnsigned Integer MAX VALUE    2147483647 getUnsigned Integer MIN VALUE    2147483648 getUnsigned Integer MIN VALUE   1    2147483649

User · Answer

There is an API for unsigned Integer and Long in Java 8

User · Answer

We needed unsigned numbers to model MySQL s unsigned TINYINT  SMALLINT  INT  BIGINT in jOOQ  which is why we have created jOOU  a minimalistic library offering wrapper types for unsigned integer numbers in Java  Example   import static org joou Unsigned        and then    UByte    b   ubyte 1   UShort   s   ushort 1   UInteger i   uint 1   ULong    l   ulong 1     All of these types extend java lang Number and can be converted into higher-order primitive types and BigInteger  Hope this helps    Disclaimer  I work for the company behind these libraries

User · Answer

Just made this piece of code  wich converts  this altura  from negative to positive number  Hope this helps someone in need         if this altura  lt  0                                String aux   Integer toString this altura                           char aux2     aux toCharArray                            aux                               for int con   1  con  lt  aux2 length  con                                 aux    aux2 con                                                     this altura   Integer parseInt aux                           System out println  New Value      this altura

User · Answer

You can use the Math abs number  function  It returns a positive number

[java] Declaring an unsigned int in Java

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