Simple division in Java - is this a bug or a feature

Question

I m trying this simple calculation in a Java application   System out println  b      1 - 7   10      Obviously I expect the output to be b 0 3  but I actually get b 1 instead   What   Why does this happen   If I write   System out println  b      1 - 0 7      I get the right result  which is b 0 3   What s going wrong here

User · Accepted Answer

You re using integer division   Try 7 0 10 instead

User · Answer

Please do not take this as an answer to the question  It is not  but an advice related to exploiting the difference of int and float  I would have put this under a comment except that the answer box allows me to format this comment   This feature has been used in every respectable programming language since the days of fortran  or earlier  - I must confess I was once a Fortran and Cobol punch card programmer   As an example  integer division of 10 3 yields integer value 3 since an integer has no facility to hold fractional residual  3333      One of the ways we  old time ancient programmers  had been using this feature is loop control   Let s say we wish to print an array of 1000 strings  but we wish to insert a line break after every 15th string  to insert some prettyfying chars at the end of the line and at the beginning of the next line  We exploit this  given that integer k is the position of a string in that array   int k 15  15    k   is true only when k is divisible by 15  an occurrence at a frequency of every 15th cell   Which is akin to what my friend said about his grandfather s dead watch being accurate twice a day   int 1 15    0 - gt  int 1 15  15   0 int 2 15    0 - gt  int 2 15  15   0     int 14 15    0 - gt  int 14 15  15   0 int 15 15    1 - gt  int 15 15  15   15  int 16 15    1 - gt  int 16 15  15   15 int 17 15    1 - gt  int 17 15  15   15     int 29 15    1 - gt  int 29 15  15   15 int 30 15    2 - gt  int 30 15  15   30   Therefore  the loop   leftPrettyfy    for int k 0  k lt sa length  k       print sa k      int z   k   1    if   z 15  15    z       rightPrettyfy        leftPrettyfy            By varying k in a fanciful way in the loop  we could print a triangular printout  1 2  3 4  5  6 7  8  9  10 11 12 13 14 15   That is to demonstrate that  if you consider this a bug  this  bug  is a useful feature that we would not want to be removed from any of the various languages that we have used thus far

User · Answer

You ve used integers in the expression 7 10  and integer 7 divided by integer 10 is zero   What you re expecting is floating point division  Any of the following would evaluate the way you expected   7 0   10 7   10 0 7 0   10 0 7    double  10

User · Answer

In my case I was doing this   double a    double   MAX BANDWIDTH SHARED MB  qCount 1      Instead of the  correct     double a    double MAX BANDWIDTH SHARED MB  qCount 1     Take attention with the parentheses

User · Answer

I find letter identifiers to be more readable and more indicative of parsed type   1 - 7f   10 1 - 7   10f   or   1 - 7d   10 1 - 7   10d

[java] Simple division in Java - is this a bug or a feature?

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