Why doesn t Java support unsigned ints

Question

Why doesn t Java include support for unsigned integers     It seems to me to be an odd omission  given that they allow one to write code that is less likely to produce overflows on unexpectedly large input     Furthermore  using unsigned integers can be a form of self-documentation  since they indicate that the value which the unsigned int was intended to hold is never supposed to be negative     Lastly  in some cases  unsigned integers can be more efficient for certain operations  such as division     What s the downside to including these

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I think Java is fine as it is  adding unsigned would complicate it without much gain  Even with the simplified integer model  most Java programmers don t know how the basic numeric types behave - just read the book Java Puzzlers to see what misconceptions you might hold   As for practical advice    If your values are somewhat arbitrary size and don t fit into int  use long  If they don t fit into long use BigInteger  Use the smaller types only for arrays when you need to save space  If you need exactly 64 32 16 8 bits  use long int short byte and stop worrying about the sign bit  except for division  comparison  right shift  and casting    See also this answer about  porting a random number generator from C to Java

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I ve heard stories that they were to be included close to the orignal Java release  Oak was the precursor to Java  and in some spec documents there was mention of usigned values  Unfortunately these never made it into the Java language  As far as anyone has been able to figure out they just didn t get implemented  likely due to a time constraint

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I once took a C   course with someone on the C   standards committee who implied that Java made the right decision to avoid having unsigned integers because  1  most programs that use unsigned integers can do just as well with signed integers and this is more natural in terms of how people think  and  2  using unsigned integers results in lots easy to create but difficult to debug issues such as integer arithmetic overflow and losing significant bits when converting between signed and unsigned types  If you mistakenly subtract 1 from 0 using signed integers it often more quickly causes your program to crash and makes it easier to find the bug than if it wraps around to 2 32 - 1  and compilers and static analysis tools and runtime checks have to assume you know what you re doing since you chose to use unsigned arithmetic  Also  negative numbers like -1 can often represent something useful  like a field being ignored defaulted unset while if you were using unsigned you d have to reserve a special value like 2 32 - 1 or something similar   Long ago  when memory was limited and processors did not automatically operate on 64 bits at once  every bit counted a lot more  so having signed vs unsigned bytes or shorts actually mattered a lot more often and was obviously the right design decision  Today just using a signed int is more than sufficient in almost all regular programming cases  and if your program really needs to use values bigger than 2 31 - 1  you often just want a long anyway  Once you re into the territory of using longs  it s even harder to come up with a reason why you really can t get by with 2 63 - 1 positive integers  Whenever we go to 128 bit processors it ll be even less of an issue

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Because unsigned type is pure evil   The fact that in C unsigned - int produces unsigned is even more evil   Here is a snapshot of the problem that burned me more than once      We have odd positive number of rays      consecutive ones at angle delta from each other  assert  rays size    gt  0  amp  amp  rays size     2    1        Get a set of ray at delta angle between them  for  size t n   0  n  lt  rays size      n            Compute the angle between nth ray and the middle one         The index of the middle one is  rays size   - 1    2         the rays are evenly spaced at angle delta  therefore        the magnitude of the angle between nth ray and the         middle one is       double angle   delta   fabs  n -  rays size   - 1    2             Do something else         Have you noticed the bug yet  I confess I only saw it after stepping in with the debugger    Because n is of unsigned type size t the entire expression n -  rays size   - 1    2 evaluates as unsigned  That expression is intended to be a signed position of the nth ray from the middle one  the 1st ray from the middle one on the left side would have position -1  the 1st one on the right would have position  1  etc  After taking abs value and multiplying by the delta angle I would get the angle between nth ray and the middle one   Unfortunately for me the above expression contained the evil unsigned and instead of evaluating to  say  -1  it evaluated to 2 32-1  The subsequent conversion to double sealed the bug   After a bug or two caused by misuse of unsigned arithmetic one has to start wondering whether the extra bit one gets is worth the extra trouble  I am trying  as much as feasible  to avoid any use of unsigned types in arithmetic  although still use it for non-arithmetic operations such as binary masks

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I can think of one unfortunate side-effect  In java embedded databases  the number of ids you can have with a 32bit id field is 2 31  not 2 32   2billion  not  4billion

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Java does have unsigned types  or at least one   char is an unsigned short   So whatever excuse Gosling throws up it s really just his ignorance why there are no other unsigned types   Also Short types   shorts are used all the time for multimedia   The reason is you can fit 2 samples in a single 32-bit unsigned long and vectorize many operations    Same thing with 8-bit data and unsigned byte   You can fit 4 or 8 samples in a register for vectorizing

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I once took a C   course with someone on the C   standards committee who implied that Java made the right decision to avoid having unsigned integers because  1  most programs that use unsigned integers can do just as well with signed integers and this is more natural in terms of how people think  and  2  using unsigned integers results in lots easy to create but difficult to debug issues such as integer arithmetic overflow and losing significant bits when converting between signed and unsigned types  If you mistakenly subtract 1 from 0 using signed integers it often more quickly causes your program to crash and makes it easier to find the bug than if it wraps around to 2 32 - 1  and compilers and static analysis tools and runtime checks have to assume you know what you re doing since you chose to use unsigned arithmetic  Also  negative numbers like -1 can often represent something useful  like a field being ignored defaulted unset while if you were using unsigned you d have to reserve a special value like 2 32 - 1 or something similar   Long ago  when memory was limited and processors did not automatically operate on 64 bits at once  every bit counted a lot more  so having signed vs unsigned bytes or shorts actually mattered a lot more often and was obviously the right design decision  Today just using a signed int is more than sufficient in almost all regular programming cases  and if your program really needs to use values bigger than 2 31 - 1  you often just want a long anyway  Once you re into the territory of using longs  it s even harder to come up with a reason why you really can t get by with 2 63 - 1 positive integers  Whenever we go to 128 bit processors it ll be even less of an issue

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As soon as signed and unsigned ints are mixed in an expression things start to get messy and you probably will lose information  Restricting Java to signed ints only really clears things up  I   m glad I don   t have to worry about the whole signed unsigned business  though I sometimes do miss the 8th bit in a byte

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Reading between the lines  I think the logic was something like this    generally  the Java designers wanted to simplify the repertoire of data types available for everyday purposes  they felt that the most common need was for signed data types for implementing certain algorithms  unsigned arithmetic is sometimes needed  but the kind of programmers that would be implementing such algorithms would also have the knowledge to  work round  doing unsigned arithmetic with signed data types   Mostly  I d say it was a reasonable decision  Possibly  I would have    made byte unsigned  or at least have provided a signed unsigned alternatives  possibly with different names  for this one data type  making it signed is good for consistency  but when do you ever need a signed byte   done away with  short   when did you last use 16-bit signed arithmetic     Still  with a bit of kludging  operations on unsigned values up to 32 bits aren t tooo bad  and most people don t need unsigned 64-bit division or comparison

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Your question is  Why doesn t Java support unsigned ints    And my answer to your question is that Java wants that all of it s primitive types  byte  char  short  int and long should be treated as byte  word  dword and qword respectively  exactly like in assembly  and the Java operators are signed operations on all of it s primitive types except for char  but only on char they are unsigned 16 bit only   So static methods suppose to be the unsigned operations also for both 32 and 64 bit   You need final class  whose static methods can be called for the unsigned operations   You can create this final class  call it whatever name you want and implement it s static methods   If you have no idea about how to implement the static methods then this link may help you   In my opinion  Java is not similar to C   at all  if it neither support unsigned types nor operator overloading  so I think that Java should be treated as completely different language from both C   and from C   It is also completely different in the name of the languages by the way   So I don t recommend in Java to type code similar to C and I don t recommend to type code similar to C   at all  because then in Java you won t be able to do what you want to do next in C    i e  the code won t continue to be C   like at all and for me this is bad to code like that  to change the style in the middle   I recommend to write and use static methods also for the signed operations  so you don t see in the code mixture of operators and static methods for both signed and unsigned operations  unless you need only signed operations in the code  and it s okay to use the operators only   Also I recommend to avoid using short  int and long primitive types  and use word  dword and qword respectively instead  and you are about call the static methods for unsigned operations and or signed operations instead of using operators   If you are about to do signed operations only and use the operators only in the code  then this is okay to use these primitive types short  int and long   Actually word  dword and qword don t exist in the language  but you can create new class for each and the implementation of each should be very easy   The class word holds the primitive type short only  the class dword holds the primitive type int only and the class qword holds the primitive type long only  Now all the unsigned and the signed methods as static or not as your choice  you can implement in each class  i e  all the 16 bit operations both unsigned and signed by giving meaning names on the word class  all the 32 bit operations both unsigned and signed by giving meaning names on the dword class and all the 64 bit operations both unsigned and signed by giving meaning names on the qword class   If you don t like giving too many different names for each method  you can always use overloading in Java  good to read that Java didn t remove that too   If you want methods rather than operators for 8 bit signed operations and methods for 8 bit unsigned operations that have no operators at all  then you can create the Byte class  note that the first letter  B  is capital  so this is not the primitive type byte  and implement the methods in this class   About passing by value and passing by reference   If I am not wrong  like in C   primitive objects are passed by value naturally  but class objects are passed by reference naturally  so that means that objects of type Byte  word  dword and qword will be passed by reference and not by value by default  I wish Java had struct objects as C  has   so all Byte  word  dword and qword could be implemented to be struct instead of class  so by default they were passed by value and not by reference by default  like any struct object in C   like the primitive types  are passed by value and not by reference by default  but because that Java is worse than C  and we have to deal with that  then there is only classes and interfaces  that are passed by reference and not by value by default  So if you want to pass Byte  word  dword and qword objects by value and not by reference  like any other class object in Java and also in C   you will have to simply use the copy constructor and that s it   That s the only solution that I can think about  I just wish that I could just typedef the primitive types to word  dword and qword  but Java neither support typedef nor using at all  unlike C  that supports using  which is equivalent to the C s typedef   About output   For the same sequence of bits  you can print them in many ways  As binary  as decimal  like the meaning of  u in C printf   as octal  like the meaning of  o in C printf   as hexadecimal  like the meaning of  x in C printf  and as integer  like the meaning of the  d in C printf    Note that C printf doesn t know the type of the variables being passed as parameters to the function  so printf knows the type of each variable only from the char  object passed to the first parameter of the function   So in each of the classes  Byte  word  dword and qword  you can implement print method and get the functionality of printf  even though the primitive type of the class is signed  you still can print it as unsigned by following some algorithm involving logical and shift operations to get the digits to print to the output   Unfortunately the link I gave you doesn t show how to implement these print methods  but I am sure you can google for the algorithms you need to implement these print methods   That s all I can answer your question and suggest you

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I ve heard stories that they were to be included close to the orignal Java release  Oak was the precursor to Java  and in some spec documents there was mention of usigned values  Unfortunately these never made it into the Java language  As far as anyone has been able to figure out they just didn t get implemented  likely due to a time constraint

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I can think of one unfortunate side-effect  In java embedded databases  the number of ids you can have with a 32bit id field is 2 31  not 2 32   2billion  not  4billion

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http   skeletoncoder blogspot com 2006 09 java-tutorials-why-no-unsigned html  This guy says because the C standard defines operations involving unsigned and signed ints to be treated as unsigned  This could cause negative signed integers to roll around into a large unsigned int  potentially causing bugs

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http   skeletoncoder blogspot com 2006 09 java-tutorials-why-no-unsigned html  This guy says because the C standard defines operations involving unsigned and signed ints to be treated as unsigned  This could cause negative signed integers to roll around into a large unsigned int  potentially causing bugs

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There s a few gems in the  C  spec that Java dropped for pragmatic reasons but which are slowly creeping back with developer demand  closures  etc    I mention a first one because it s related to this discussion  the adherence of pointer values to unsigned integer arithmetic  And  in relation to this thread topic  the difficulty of maintaining Unsigned semantics in the Signed world of Java   I would guess if one were to get a Dennis Ritchie alter ego to advise Gosling s design team it would have suggested giving Signed s a  zero at infinity   so that all address offset requests would first add their ALGEBRAIC RING SIZE to obviate negative values   That way  any offset thrown at the array can never generate a SEGFAULT  For example in an encapsulated class which I call RingArray of doubles that needs unsigned behaviour - in  self rotating loop  context             Housekeeping state variable long entrycount         A sequence number int cycle               Number of loops cycled int size                Active size of the array because size lt modulus during cycle 0 int modulus             Maximal size of the array     Ring state variables private int head       The  head  of the Ring private int tail       The ring iterator  cursor     tail may get the current cursor position    and head gets the old tail value    there are other semantic variations possible     The Array state variable double    darray        The array of doubles     somewhere in constructor public RingArray int modulus        super        this modulus   modulus      tail    head    cycle   0      darray   new double modulus                   double getElementAt int offset       return darray  tail modulus offset modulus  modulus         remember  the above is treating steady-state where size  modulus          The above RingArray would never ever  get  from a negative index  even if a malicious requestor tried to  Remember  there are also many legitimate requests for asking for prior  negative  index values   NB  The outer  modulus de-references legitimate requests whereas the inner  modulus masks out blatant malice from negatives more negative than -modulus  If this were to ever appear in a Java     9    8     spec  then the problem would genuinely become a  programmer who cannot  self rotate  FAULT    I m sure the so-called Java unsigned int  deficiency  can be made up for with the above one-liner   PS  Just to give context to above RingArray housekeeping  here s a candidate  set  operation to match the above  get  element operation   void addElement long entrycount double value      to be called only by the keeper of entrycount     this entrycount  entrycount      cycle    int entrycount modulus      if cycle  0                            start-up is when the ring is being populated the first time around         size    int entrycount             during start-up  size is less than modulus so use modulo size arithmetic         tail    int entrycount size         during start-up           else           size   modulus          head   tail          tail    int entrycount modulus      after start-up           darray head    value                    always overwrite old tail

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This is from an interview with Gosling and others  about simplicity      Gosling  For me as a language designer  which I don t really count myself as these days  what  simple  really ended up meaning was could I expect J  Random Developer to hold the spec in his head  That definition says that  for instance  Java isn t -- and in fact a lot of these languages end up with a lot of corner cases  things that nobody really understands  Quiz any C developer about unsigned  and pretty soon you discover that almost no C developers actually understand what goes on with unsigned  what unsigned arithmetic is  Things like that made C complex  The language part of Java is  I think  pretty simple  The libraries you have to look up

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I know this post is too old  however for your interest  in Java 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 232-1  Use the Integer class to use int data type as an unsigned integer and static methods like compareUnsigned    divideUnsigned   etc  have been added to the Integer class to support the arithmetic operations for unsigned integers

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As soon as signed and unsigned ints are mixed in an expression things start to get messy and you probably will lose information  Restricting Java to signed ints only really clears things up  I   m glad I don   t have to worry about the whole signed unsigned business  though I sometimes do miss the 8th bit in a byte

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Your question is  Why doesn t Java support unsigned ints    And my answer to your question is that Java wants that all of it s primitive types  byte  char  short  int and long should be treated as byte  word  dword and qword respectively  exactly like in assembly  and the Java operators are signed operations on all of it s primitive types except for char  but only on char they are unsigned 16 bit only   So static methods suppose to be the unsigned operations also for both 32 and 64 bit   You need final class  whose static methods can be called for the unsigned operations   You can create this final class  call it whatever name you want and implement it s static methods   If you have no idea about how to implement the static methods then this link may help you   In my opinion  Java is not similar to C   at all  if it neither support unsigned types nor operator overloading  so I think that Java should be treated as completely different language from both C   and from C   It is also completely different in the name of the languages by the way   So I don t recommend in Java to type code similar to C and I don t recommend to type code similar to C   at all  because then in Java you won t be able to do what you want to do next in C    i e  the code won t continue to be C   like at all and for me this is bad to code like that  to change the style in the middle   I recommend to write and use static methods also for the signed operations  so you don t see in the code mixture of operators and static methods for both signed and unsigned operations  unless you need only signed operations in the code  and it s okay to use the operators only   Also I recommend to avoid using short  int and long primitive types  and use word  dword and qword respectively instead  and you are about call the static methods for unsigned operations and or signed operations instead of using operators   If you are about to do signed operations only and use the operators only in the code  then this is okay to use these primitive types short  int and long   Actually word  dword and qword don t exist in the language  but you can create new class for each and the implementation of each should be very easy   The class word holds the primitive type short only  the class dword holds the primitive type int only and the class qword holds the primitive type long only  Now all the unsigned and the signed methods as static or not as your choice  you can implement in each class  i e  all the 16 bit operations both unsigned and signed by giving meaning names on the word class  all the 32 bit operations both unsigned and signed by giving meaning names on the dword class and all the 64 bit operations both unsigned and signed by giving meaning names on the qword class   If you don t like giving too many different names for each method  you can always use overloading in Java  good to read that Java didn t remove that too   If you want methods rather than operators for 8 bit signed operations and methods for 8 bit unsigned operations that have no operators at all  then you can create the Byte class  note that the first letter  B  is capital  so this is not the primitive type byte  and implement the methods in this class   About passing by value and passing by reference   If I am not wrong  like in C   primitive objects are passed by value naturally  but class objects are passed by reference naturally  so that means that objects of type Byte  word  dword and qword will be passed by reference and not by value by default  I wish Java had struct objects as C  has   so all Byte  word  dword and qword could be implemented to be struct instead of class  so by default they were passed by value and not by reference by default  like any struct object in C   like the primitive types  are passed by value and not by reference by default  but because that Java is worse than C  and we have to deal with that  then there is only classes and interfaces  that are passed by reference and not by value by default  So if you want to pass Byte  word  dword and qword objects by value and not by reference  like any other class object in Java and also in C   you will have to simply use the copy constructor and that s it   That s the only solution that I can think about  I just wish that I could just typedef the primitive types to word  dword and qword  but Java neither support typedef nor using at all  unlike C  that supports using  which is equivalent to the C s typedef   About output   For the same sequence of bits  you can print them in many ways  As binary  as decimal  like the meaning of  u in C printf   as octal  like the meaning of  o in C printf   as hexadecimal  like the meaning of  x in C printf  and as integer  like the meaning of the  d in C printf    Note that C printf doesn t know the type of the variables being passed as parameters to the function  so printf knows the type of each variable only from the char  object passed to the first parameter of the function   So in each of the classes  Byte  word  dword and qword  you can implement print method and get the functionality of printf  even though the primitive type of the class is signed  you still can print it as unsigned by following some algorithm involving logical and shift operations to get the digits to print to the output   Unfortunately the link I gave you doesn t show how to implement these print methods  but I am sure you can google for the algorithms you need to implement these print methods   That s all I can answer your question and suggest you

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With JDK8 it does have some support for them   We may yet see full support of unsigned types in Java despite Gosling s concerns

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This is from an interview with Gosling and others  about simplicity      Gosling  For me as a language designer  which I don t really count myself as these days  what  simple  really ended up meaning was could I expect J  Random Developer to hold the spec in his head  That definition says that  for instance  Java isn t -- and in fact a lot of these languages end up with a lot of corner cases  things that nobody really understands  Quiz any C developer about unsigned  and pretty soon you discover that almost no C developers actually understand what goes on with unsigned  what unsigned arithmetic is  Things like that made C complex  The language part of Java is  I think  pretty simple  The libraries you have to look up

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The reason IMHO is because they are were too lazy to implement correct that mistake   Suggesting that C C   programmers does not understand unsigned  structure  union  bit flag    Is just preposterous   Ether you were talking with a basic bash java programmer on the verge of beginning programming a la C  without any real knowledge this language or you are just talking out of your own mind      when you deal every day on format either from file or hardware you begin to question  what in the hell they were thinking   A good example here would be trying to use an unsigned byte as a self rotating loop   For those of you who do not understand the last sentence  how on earth you call yourself a programmer    DC

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I think Java is fine as it is  adding unsigned would complicate it without much gain  Even with the simplified integer model  most Java programmers don t know how the basic numeric types behave - just read the book Java Puzzlers to see what misconceptions you might hold   As for practical advice    If your values are somewhat arbitrary size and don t fit into int  use long  If they don t fit into long use BigInteger  Use the smaller types only for arrays when you need to save space  If you need exactly 64 32 16 8 bits  use long int short byte and stop worrying about the sign bit  except for division  comparison  right shift  and casting    See also this answer about  porting a random number generator from C to Java

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This is an older question and pat did briefly mention char  I just thought I should expand upon this for others who will look at this down the road  Let s take a closer look at the Java primitive types   byte - 8-bit signed integer  short - 16-bit signed integer  int - 32-bit signed integer  long - 64-bit signed integer  char - 16-bit character  unsigned integer   Although char does not support unsigned arithmetic  it essentially can be treated as an unsigned integer  You would have to explicitly cast arithmetic operations back into char  but it does provide you with a way to specify unsigned numbers   char a   0  char b   6  a    1  a    char   a   b   a    char   a   b   a    char   a - 16   b    char   b   3   b    char   b   a     a   -1     Generates complier error  must be cast to char System out println a      Prints    System out println  int  a      Prints 65532 System out println  short  a      Prints -4 short c   -4  System out println  int  c      Prints -4  notice the difference with char a    2  a -  6  a    3  a    7  a    a--    Yes  there isn t direct support for unsigned integers  obviously  I wouldn t have to cast most of my operations back into char if there was direct support   However  there certainly exists an unsigned primitive data type  I would liked to have seen an unsigned byte as well  but I guess doubling the memory cost and instead use char is a viable option     Edit  With JDK8 there are new APIs for Long and Integer which provide helper methods when treating long and int values as unsigned values    compareUnsigned divideUnsigned parseUnsignedInt parseUnsignedLong remainderUnsigned toUnsignedLong toUnsignedString   Additionally  Guava provides a number of helper methods to do similar things for at the integer types which helps close the gap left by the lack of native support for unsigned integers

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I ve heard stories that they were to be included close to the orignal Java release  Oak was the precursor to Java  and in some spec documents there was mention of usigned values  Unfortunately these never made it into the Java language  As far as anyone has been able to figure out they just didn t get implemented  likely due to a time constraint

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There s a few gems in the  C  spec that Java dropped for pragmatic reasons but which are slowly creeping back with developer demand  closures  etc    I mention a first one because it s related to this discussion  the adherence of pointer values to unsigned integer arithmetic  And  in relation to this thread topic  the difficulty of maintaining Unsigned semantics in the Signed world of Java   I would guess if one were to get a Dennis Ritchie alter ego to advise Gosling s design team it would have suggested giving Signed s a  zero at infinity   so that all address offset requests would first add their ALGEBRAIC RING SIZE to obviate negative values   That way  any offset thrown at the array can never generate a SEGFAULT  For example in an encapsulated class which I call RingArray of doubles that needs unsigned behaviour - in  self rotating loop  context             Housekeeping state variable long entrycount         A sequence number int cycle               Number of loops cycled int size                Active size of the array because size lt modulus during cycle 0 int modulus             Maximal size of the array     Ring state variables private int head       The  head  of the Ring private int tail       The ring iterator  cursor     tail may get the current cursor position    and head gets the old tail value    there are other semantic variations possible     The Array state variable double    darray        The array of doubles     somewhere in constructor public RingArray int modulus        super        this modulus   modulus      tail    head    cycle   0      darray   new double modulus                   double getElementAt int offset       return darray  tail modulus offset modulus  modulus         remember  the above is treating steady-state where size  modulus          The above RingArray would never ever  get  from a negative index  even if a malicious requestor tried to  Remember  there are also many legitimate requests for asking for prior  negative  index values   NB  The outer  modulus de-references legitimate requests whereas the inner  modulus masks out blatant malice from negatives more negative than -modulus  If this were to ever appear in a Java     9    8     spec  then the problem would genuinely become a  programmer who cannot  self rotate  FAULT    I m sure the so-called Java unsigned int  deficiency  can be made up for with the above one-liner   PS  Just to give context to above RingArray housekeeping  here s a candidate  set  operation to match the above  get  element operation   void addElement long entrycount double value      to be called only by the keeper of entrycount     this entrycount  entrycount      cycle    int entrycount modulus      if cycle  0                            start-up is when the ring is being populated the first time around         size    int entrycount             during start-up  size is less than modulus so use modulo size arithmetic         tail    int entrycount size         during start-up           else           size   modulus          head   tail          tail    int entrycount modulus      after start-up           darray head    value                    always overwrite old tail

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This is an older question and pat did briefly mention char  I just thought I should expand upon this for others who will look at this down the road  Let s take a closer look at the Java primitive types   byte - 8-bit signed integer  short - 16-bit signed integer  int - 32-bit signed integer  long - 64-bit signed integer  char - 16-bit character  unsigned integer   Although char does not support unsigned arithmetic  it essentially can be treated as an unsigned integer  You would have to explicitly cast arithmetic operations back into char  but it does provide you with a way to specify unsigned numbers   char a   0  char b   6  a    1  a    char   a   b   a    char   a   b   a    char   a - 16   b    char   b   3   b    char   b   a     a   -1     Generates complier error  must be cast to char System out println a      Prints    System out println  int  a      Prints 65532 System out println  short  a      Prints -4 short c   -4  System out println  int  c      Prints -4  notice the difference with char a    2  a -  6  a    3  a    7  a    a--    Yes  there isn t direct support for unsigned integers  obviously  I wouldn t have to cast most of my operations back into char if there was direct support   However  there certainly exists an unsigned primitive data type  I would liked to have seen an unsigned byte as well  but I guess doubling the memory cost and instead use char is a viable option     Edit  With JDK8 there are new APIs for Long and Integer which provide helper methods when treating long and int values as unsigned values    compareUnsigned divideUnsigned parseUnsignedInt parseUnsignedLong remainderUnsigned toUnsignedLong toUnsignedString   Additionally  Guava provides a number of helper methods to do similar things for at the integer types which helps close the gap left by the lack of native support for unsigned integers

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With JDK8 it does have some support for them   We may yet see full support of unsigned types in Java despite Gosling s concerns

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This is from an interview with Gosling and others  about simplicity      Gosling  For me as a language designer  which I don t really count myself as these days  what  simple  really ended up meaning was could I expect J  Random Developer to hold the spec in his head  That definition says that  for instance  Java isn t -- and in fact a lot of these languages end up with a lot of corner cases  things that nobody really understands  Quiz any C developer about unsigned  and pretty soon you discover that almost no C developers actually understand what goes on with unsigned  what unsigned arithmetic is  Things like that made C complex  The language part of Java is  I think  pretty simple  The libraries you have to look up

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The reason IMHO is because they are were too lazy to implement correct that mistake   Suggesting that C C   programmers does not understand unsigned  structure  union  bit flag    Is just preposterous   Ether you were talking with a basic bash java programmer on the verge of beginning programming a la C  without any real knowledge this language or you are just talking out of your own mind      when you deal every day on format either from file or hardware you begin to question  what in the hell they were thinking   A good example here would be trying to use an unsigned byte as a self rotating loop   For those of you who do not understand the last sentence  how on earth you call yourself a programmer    DC

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I can think of one unfortunate side-effect  In java embedded databases  the number of ids you can have with a 32bit id field is 2 31  not 2 32   2billion  not  4billion

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Reading between the lines  I think the logic was something like this    generally  the Java designers wanted to simplify the repertoire of data types available for everyday purposes  they felt that the most common need was for signed data types for implementing certain algorithms  unsigned arithmetic is sometimes needed  but the kind of programmers that would be implementing such algorithms would also have the knowledge to  work round  doing unsigned arithmetic with signed data types   Mostly  I d say it was a reasonable decision  Possibly  I would have    made byte unsigned  or at least have provided a signed unsigned alternatives  possibly with different names  for this one data type  making it signed is good for consistency  but when do you ever need a signed byte   done away with  short   when did you last use 16-bit signed arithmetic     Still  with a bit of kludging  operations on unsigned values up to 32 bits aren t tooo bad  and most people don t need unsigned 64-bit division or comparison

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I know this post is too old  however for your interest  in Java 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 232-1  Use the Integer class to use int data type as an unsigned integer and static methods like compareUnsigned    divideUnsigned   etc  have been added to the Integer class to support the arithmetic operations for unsigned integers

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I think Java is fine as it is  adding unsigned would complicate it without much gain  Even with the simplified integer model  most Java programmers don t know how the basic numeric types behave - just read the book Java Puzzlers to see what misconceptions you might hold   As for practical advice    If your values are somewhat arbitrary size and don t fit into int  use long  If they don t fit into long use BigInteger  Use the smaller types only for arrays when you need to save space  If you need exactly 64 32 16 8 bits  use long int short byte and stop worrying about the sign bit  except for division  comparison  right shift  and casting    See also this answer about  porting a random number generator from C to Java

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http   skeletoncoder blogspot com 2006 09 java-tutorials-why-no-unsigned html  This guy says because the C standard defines operations involving unsigned and signed ints to be treated as unsigned  This could cause negative signed integers to roll around into a large unsigned int  potentially causing bugs

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I ve heard stories that they were to be included close to the orignal Java release  Oak was the precursor to Java  and in some spec documents there was mention of usigned values  Unfortunately these never made it into the Java language  As far as anyone has been able to figure out they just didn t get implemented  likely due to a time constraint

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Reading between the lines  I think the logic was something like this    generally  the Java designers wanted to simplify the repertoire of data types available for everyday purposes  they felt that the most common need was for signed data types for implementing certain algorithms  unsigned arithmetic is sometimes needed  but the kind of programmers that would be implementing such algorithms would also have the knowledge to  work round  doing unsigned arithmetic with signed data types   Mostly  I d say it was a reasonable decision  Possibly  I would have    made byte unsigned  or at least have provided a signed unsigned alternatives  possibly with different names  for this one data type  making it signed is good for consistency  but when do you ever need a signed byte   done away with  short   when did you last use 16-bit signed arithmetic     Still  with a bit of kludging  operations on unsigned values up to 32 bits aren t tooo bad  and most people don t need unsigned 64-bit division or comparison

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I can think of one unfortunate side-effect  In java embedded databases  the number of ids you can have with a 32bit id field is 2 31  not 2 32   2billion  not  4billion

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I think Java is fine as it is  adding unsigned would complicate it without much gain  Even with the simplified integer model  most Java programmers don t know how the basic numeric types behave - just read the book Java Puzzlers to see what misconceptions you might hold   As for practical advice    If your values are somewhat arbitrary size and don t fit into int  use long  If they don t fit into long use BigInteger  Use the smaller types only for arrays when you need to save space  If you need exactly 64 32 16 8 bits  use long int short byte and stop worrying about the sign bit  except for division  comparison  right shift  and casting    See also this answer about  porting a random number generator from C to Java

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This is from an interview with Gosling and others  about simplicity      Gosling  For me as a language designer  which I don t really count myself as these days  what  simple  really ended up meaning was could I expect J  Random Developer to hold the spec in his head  That definition says that  for instance  Java isn t -- and in fact a lot of these languages end up with a lot of corner cases  things that nobody really understands  Quiz any C developer about unsigned  and pretty soon you discover that almost no C developers actually understand what goes on with unsigned  what unsigned arithmetic is  Things like that made C complex  The language part of Java is  I think  pretty simple  The libraries you have to look up

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As soon as signed and unsigned ints are mixed in an expression things start to get messy and you probably will lose information  Restricting Java to signed ints only really clears things up  I   m glad I don   t have to worry about the whole signed unsigned business  though I sometimes do miss the 8th bit in a byte

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Because unsigned type is pure evil   The fact that in C unsigned - int produces unsigned is even more evil   Here is a snapshot of the problem that burned me more than once      We have odd positive number of rays      consecutive ones at angle delta from each other  assert  rays size    gt  0  amp  amp  rays size     2    1        Get a set of ray at delta angle between them  for  size t n   0  n  lt  rays size      n            Compute the angle between nth ray and the middle one         The index of the middle one is  rays size   - 1    2         the rays are evenly spaced at angle delta  therefore        the magnitude of the angle between nth ray and the         middle one is       double angle   delta   fabs  n -  rays size   - 1    2             Do something else         Have you noticed the bug yet  I confess I only saw it after stepping in with the debugger    Because n is of unsigned type size t the entire expression n -  rays size   - 1    2 evaluates as unsigned  That expression is intended to be a signed position of the nth ray from the middle one  the 1st ray from the middle one on the left side would have position -1  the 1st one on the right would have position  1  etc  After taking abs value and multiplying by the delta angle I would get the angle between nth ray and the middle one   Unfortunately for me the above expression contained the evil unsigned and instead of evaluating to  say  -1  it evaluated to 2 32-1  The subsequent conversion to double sealed the bug   After a bug or two caused by misuse of unsigned arithmetic one has to start wondering whether the extra bit one gets is worth the extra trouble  I am trying  as much as feasible  to avoid any use of unsigned types in arithmetic  although still use it for non-arithmetic operations such as binary masks

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Java does have unsigned types  or at least one   char is an unsigned short   So whatever excuse Gosling throws up it s really just his ignorance why there are no other unsigned types   Also Short types   shorts are used all the time for multimedia   The reason is you can fit 2 samples in a single 32-bit unsigned long and vectorize many operations    Same thing with 8-bit data and unsigned byte   You can fit 4 or 8 samples in a register for vectorizing

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http   skeletoncoder blogspot com 2006 09 java-tutorials-why-no-unsigned html  This guy says because the C standard defines operations involving unsigned and signed ints to be treated as unsigned  This could cause negative signed integers to roll around into a large unsigned int  potentially causing bugs

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As soon as signed and unsigned ints are mixed in an expression things start to get messy and you probably will lose information  Restricting Java to signed ints only really clears things up  I   m glad I don   t have to worry about the whole signed unsigned business  though I sometimes do miss the 8th bit in a byte

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Reading between the lines  I think the logic was something like this    generally  the Java designers wanted to simplify the repertoire of data types available for everyday purposes  they felt that the most common need was for signed data types for implementing certain algorithms  unsigned arithmetic is sometimes needed  but the kind of programmers that would be implementing such algorithms would also have the knowledge to  work round  doing unsigned arithmetic with signed data types   Mostly  I d say it was a reasonable decision  Possibly  I would have    made byte unsigned  or at least have provided a signed unsigned alternatives  possibly with different names  for this one data type  making it signed is good for consistency  but when do you ever need a signed byte   done away with  short   when did you last use 16-bit signed arithmetic     Still  with a bit of kludging  operations on unsigned values up to 32 bits aren t tooo bad  and most people don t need unsigned 64-bit division or comparison

[java] Why doesn't Java support unsigned ints?

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