What s the syntax for mod in java

Question

As an example in pseudocode   if   a mod 2     0        isEven   true    else       isEven   false

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Java actually has no modulo operator the way C does    in Java is a remainder operator  On positive integers  it works exactly like modulo  but it works differently on negative integers and  unlike modulo  can work with floating point numbers as well  Still  it s rare to use   on anything but positive integers  so if you want to call it a modulo  then feel free

User · Answer

The remainder operator in Java is   and the modulo operator can be expressed as  public int mod int i  int j      int rem   i   j    if  j  lt  0  amp  amp  rem  gt  0          return rem   j        if  j  gt  0  amp  amp  rem  lt  0          return rem   j        return rem

User · Answer

Instead of the modulo operator  which has slightly different semantics  for non-negative integers  you can use the remainder operator    For your exact example   if   a   2     0        isEven   true    else       isEven   false      This can be simplified to a one-liner   isEven    a   2     0

User · Answer

if  a   2    0      else

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The code runs much faster without using modulo   public boolean isEven int a       return    a  amp  1     0       public boolean isOdd int a       return    a  amp  1     1

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you should examine the specification before using  remainder  operator      http   java sun com docs books jls third edition html expressions html 15 17 3     bad enough implementation of isEven method  for fun  so any worse  boolean isEven int num        num    10      if num    1         return false      else if num    0         return true      else        return isEven num   2     isEven   isEven a

User · Answer

The modulo operator is    percent sign   To test for evenness or generally do modulo for a power of 2  you can also use  amp   the and operator  like isEven      a  amp  1

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The code runs much faster without using modulo   public boolean isEven int a       return    a  amp  1     0       public boolean isOdd int a       return    a  amp  1     1

User · Answer

As others have pointed out  the    remainder  operator is not the same as the mathematical mod modulus operation function      mod vs        The x mod n function maps x to n in the range of  0 n     Whereas the x   n operator maps x to n in the range of  -n n     In order to have a method to use the mathematical modulus operation and not  care about the sign in front of x one can use     x   n    n    n   Maybe this picture helps understand it better  I had a hard time wrapping my head around this first

User · Answer

Since everyone else already gave the answer  I ll add a bit of additional context    the  modulus  operator is actually performing the remainder operation   The difference between mod and rem is subtle  but important    -1 mod 2  would normally give 1   More specifically given two integers  X and Y  the operation  X mod Y  tends to return a value in the range  0  Y    Said differently  the modulus of X and Y is always greater than or equal to zero  and less than Y   Performing the same operation with the     or rem operator maintains the sign of the X value  If X is negative you get a result in the range  -Y  0    If X is positive you get a result in the range  0  Y      Often this subtle distinction doesn t matter   Going back to your code question  though  there are multiple ways of solving for  evenness    The first approach is good for beginners  because it is especially verbose      Option 1  Clearest way for beginners boolean isEven  if   a   2     0      isEven   true   else     isEven   false     The second approach takes better advantage of the language  and leads to more succinct code   Don t forget that the    operator returns a boolean       Option 2  Clear  succinct  code boolean isEven     a   2     0     The third approach is here for completeness  and uses the ternary operator   Although the ternary operator is often very useful  in this case I consider the second approach superior      Option 3  Ternary operator boolean isEven     a   2     0    true   false    The fourth and final approach is to use knowledge of the binary representation of integers   If the least significant bit is 0 then the number is even   This can be checked using the bitwise-and operator   amp     While this approach is the fastest  you are doing simple bit masking instead of division   it is perhaps a little advanced complicated for a beginner      Option 4  Bitwise-and boolean isEven     a  amp  1     0     Here I used the bitwise-and operator  and represented it in the succinct form shown in option 2   Rewriting it in Option 1 s form  and alternatively Option 3 s  is left as an exercise to the reader      Hope that helps

User · Answer

Also  mod can be used like this   int a   7  b   a   2    b would equal 1   Because 7   2   1

User · Answer

Instead of the modulo operator  which has slightly different semantics  for non-negative integers  you can use the remainder operator    For your exact example   if   a   2     0        isEven   true    else       isEven   false      This can be simplified to a one-liner   isEven    a   2     0

User · Answer

An alternative to the code from  Cody    Using the modulus operator   bool isEven    a   2     0    I think this is marginally better code than writing if else  because there is less duplication  amp  unused flexibility   It does require a bit more brain power to examine  but the good naming of isEven compensates

User · Answer

Here is the representation of your pseudo-code in minimal Java code   boolean isEven   a   2    0    I ll now break it down into its components  The modulus operator in Java is the percent character      Therefore taking an int   int returns another int  The double equals      operator is used to compare values  such as a pair of ints and returns a boolean  This is then assigned to the boolean variable  isEven   Based on operator precedence the modulus will be evaluated before the comparison

User · Answer

Since everyone else already gave the answer  I ll add a bit of additional context    the  modulus  operator is actually performing the remainder operation   The difference between mod and rem is subtle  but important    -1 mod 2  would normally give 1   More specifically given two integers  X and Y  the operation  X mod Y  tends to return a value in the range  0  Y    Said differently  the modulus of X and Y is always greater than or equal to zero  and less than Y   Performing the same operation with the     or rem operator maintains the sign of the X value  If X is negative you get a result in the range  -Y  0    If X is positive you get a result in the range  0  Y      Often this subtle distinction doesn t matter   Going back to your code question  though  there are multiple ways of solving for  evenness    The first approach is good for beginners  because it is especially verbose      Option 1  Clearest way for beginners boolean isEven  if   a   2     0      isEven   true   else     isEven   false     The second approach takes better advantage of the language  and leads to more succinct code   Don t forget that the    operator returns a boolean       Option 2  Clear  succinct  code boolean isEven     a   2     0     The third approach is here for completeness  and uses the ternary operator   Although the ternary operator is often very useful  in this case I consider the second approach superior      Option 3  Ternary operator boolean isEven     a   2     0    true   false    The fourth and final approach is to use knowledge of the binary representation of integers   If the least significant bit is 0 then the number is even   This can be checked using the bitwise-and operator   amp     While this approach is the fastest  you are doing simple bit masking instead of division   it is perhaps a little advanced complicated for a beginner      Option 4  Bitwise-and boolean isEven     a  amp  1     0     Here I used the bitwise-and operator  and represented it in the succinct form shown in option 2   Rewriting it in Option 1 s form  and alternatively Option 3 s  is left as an exercise to the reader      Hope that helps

User · Answer

if  a   2    0      else

User · Answer

if  a   2    0      else

User · Answer

An alternative to the code from  Cody    Using the modulus operator   bool isEven    a   2     0    I think this is marginally better code than writing if else  because there is less duplication  amp  unused flexibility   It does require a bit more brain power to examine  but the good naming of isEven compensates

User · Answer

The modulo operator is    percent sign   To test for evenness or generally do modulo for a power of 2  you can also use  amp   the and operator  like isEven      a  amp  1

User · Answer

Here is the representation of your pseudo-code in minimal Java code   boolean isEven   a   2    0    I ll now break it down into its components  The modulus operator in Java is the percent character      Therefore taking an int   int returns another int  The double equals      operator is used to compare values  such as a pair of ints and returns a boolean  This is then assigned to the boolean variable  isEven   Based on operator precedence the modulus will be evaluated before the comparison

User · Answer

if  a   2    0      else

User · Answer

The modulo operator is    percent sign   To test for evenness or generally do modulo for a power of 2  you can also use  amp   the and operator  like isEven      a  amp  1

User · Answer

Also  mod can be used like this   int a   7  b   a   2    b would equal 1   Because 7   2   1

User · Answer

In Java  the mod operation can be performed as such   Math floorMod a  b    Note  The mod operation is different from the remainder operation  In Java  the remainder operation can be performed as such   a   b

User · Answer

Another way is   boolean isEven   false  if  a   2     0        isEven   true      But easiest way is still    boolean isEven    a   2     0    Like  Steve Kuo said

User · Answer

Instead of the modulo operator  which has slightly different semantics  for non-negative integers  you can use the remainder operator    For your exact example   if   a   2     0        isEven   true    else       isEven   false      This can be simplified to a one-liner   isEven    a   2     0

User · Answer

An alternative to the code from  Cody    Using the modulus operator   bool isEven    a   2     0    I think this is marginally better code than writing if else  because there is less duplication  amp  unused flexibility   It does require a bit more brain power to examine  but the good naming of isEven compensates

User · Answer

Instead of the modulo operator  which has slightly different semantics  for non-negative integers  you can use the remainder operator    For your exact example   if   a   2     0        isEven   true    else       isEven   false      This can be simplified to a one-liner   isEven    a   2     0

User · Answer

An alternative to the code from  Cody    Using the modulus operator   bool isEven    a   2     0    I think this is marginally better code than writing if else  because there is less duplication  amp  unused flexibility   It does require a bit more brain power to examine  but the good naming of isEven compensates

User · Answer

To get Java s    REM  operation to work like MOD for negative X and positive Y values  you can use this method   private int mod int x  int y        int result   x   y      if  result  lt  0                result    y            return result      or with the ternary operator  shorter  but not possible or less efficient in some situations    private int mod int x  int y        int result   x   y      return result  lt  0  result   y   result

User · Answer

The remainder operator in Java is   and the modulo operator can be expressed as  public int mod int i  int j      int rem   i   j    if  j  lt  0  amp  amp  rem  gt  0          return rem   j        if  j  gt  0  amp  amp  rem  lt  0          return rem   j        return rem

User · Answer

In Java it is the   operator  15 17 3  Remainder Operator    Note that there is also floorMod in the java lang Math class which will give a different result from   for arguments with different signs   public static int floorMod  int x  int y

User · Answer

you should examine the specification before using  remainder  operator      http   java sun com docs books jls third edition html expressions html 15 17 3     bad enough implementation of isEven method  for fun  so any worse  boolean isEven int num        num    10      if num    1         return false      else if num    0         return true      else        return isEven num   2     isEven   isEven a

User · Answer

As others have pointed out  the    remainder  operator is not the same as the mathematical mod modulus operation function      mod vs        The x mod n function maps x to n in the range of  0 n     Whereas the x   n operator maps x to n in the range of  -n n     In order to have a method to use the mathematical modulus operation and not  care about the sign in front of x one can use     x   n    n    n   Maybe this picture helps understand it better  I had a hard time wrapping my head around this first

User · Answer

While it s possible to do a proper modulo by checking whether the value is negative and correct it if it is  the way many have suggested   there is a more compact solution    a   b   b    b   This will first do the modulo  limiting the value to the -b -   b range and then add b in order to ensure that the value is positive  letting the next modulo limit it to the 0 -  b range   Note  If b is negative  the result will also be negative

User · Answer

Here is the representation of your pseudo-code in minimal Java code   boolean isEven   a   2    0    I ll now break it down into its components  The modulus operator in Java is the percent character      Therefore taking an int   int returns another int  The double equals      operator is used to compare values  such as a pair of ints and returns a boolean  This is then assigned to the boolean variable  isEven   Based on operator precedence the modulus will be evaluated before the comparison

User · Answer

In Java  the mod operation can be performed as such   Math floorMod a  b    Note  The mod operation is different from the remainder operation  In Java  the remainder operation can be performed as such   a   b

User · Answer

In Java it is the   operator  15 17 3  Remainder Operator    Note that there is also floorMod in the java lang Math class which will give a different result from   for arguments with different signs   public static int floorMod  int x  int y

User · Answer

Also  mod can be used like this   int a   7  b   a   2    b would equal 1   Because 7   2   1

User · Answer

To get Java s    REM  operation to work like MOD for negative X and positive Y values  you can use this method   private int mod int x  int y        int result   x   y      if  result  lt  0                result    y            return result      or with the ternary operator  shorter  but not possible or less efficient in some situations    private int mod int x  int y        int result   x   y      return result  lt  0  result   y   result

User · Answer

While it s possible to do a proper modulo by checking whether the value is negative and correct it if it is  the way many have suggested   there is a more compact solution    a   b   b    b   This will first do the modulo  limiting the value to the -b -   b range and then add b in order to ensure that the value is positive  letting the next modulo limit it to the 0 -  b range   Note  If b is negative  the result will also be negative

User · Answer

The modulo operator is    percent sign   To test for evenness or generally do modulo for a power of 2  you can also use  amp   the and operator  like isEven      a  amp  1

User · Answer

Java actually has no modulo operator the way C does    in Java is a remainder operator  On positive integers  it works exactly like modulo  but it works differently on negative integers and  unlike modulo  can work with floating point numbers as well  Still  it s rare to use   on anything but positive integers  so if you want to call it a modulo  then feel free

User · Answer

Also  mod can be used like this   int a   7  b   a   2    b would equal 1   Because 7   2   1

User · Answer

Here is the representation of your pseudo-code in minimal Java code   boolean isEven   a   2    0    I ll now break it down into its components  The modulus operator in Java is the percent character      Therefore taking an int   int returns another int  The double equals      operator is used to compare values  such as a pair of ints and returns a boolean  This is then assigned to the boolean variable  isEven   Based on operator precedence the modulus will be evaluated before the comparison

User · Answer

Another way is   boolean isEven   false  if  a   2     0        isEven   true      But easiest way is still    boolean isEven    a   2     0    Like  Steve Kuo said

[java] What's the syntax for mod in java

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