Check whether number is even or odd

Question

How would I determine whether a given number is even or odd  I ve been wanting to figure this out for a long time now and haven t gotten anywhere

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If the remainder when you divide by 2 is 0  it s even    is the operator to get a remainder

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Check if a number is even or not using modulus operator                 param number the number to be checked          return   code true  if the given number is even  otherwise   code false               public static boolean isEven int number            return number   2    0                        Check if a number is even or not using  amp  operator                 param number the number to be checked          return   code true  if the given number is even  otherwise   code false               public static boolean isEvenFaster int number            return  number  amp  1     0         source

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Least significant bit  rightmost  can be used to check if the number is even or odd  For all Odd numbers  rightmost bit is always 1 in binary representation   public static boolean checkOdd long number      return   number  amp  0x1     1

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Every even number is divisible by two  regardless of if it s a decimal  but the decimal  if present  must also be even   So you can use the    modulo  operator  which divides the number on the left by the number on the right and returns the remainder     boolean isEven double num    return   num   2     0

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You can use the modulus operator  but that can be slow  If it s an integer  you can do   if    x  amp  1     0     even      else   odd        This is because the low bit will always be set on an odd number

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package isevenodd  import java util Scanner  public class IsEvenOdd       public static void main String   args            Scanner scan   new Scanner System in           System out println  Enter number              int y   scan nextInt                   boolean isEven    y   2    0    true   false          String x    isEven     even     odd             System out println  Your number is     x

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You can use the modulus operator  but that can be slow  A more efficient way would be to check the lowest bit because that determines whether a number is even or odd  The code would look something like this   public static void main String   args                System out println  Enter a number to check if it is even or odd                System out println  Your number is        new Scanner System in  nextInt    amp  1     0     even     odd

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Works for positive or negative numbers     int start   -3  int end   6   for  int val   start  val  lt  end  val             Condition to Check Even  Not condition     will give Odd number     if  val   2    0                 System out println  Even    val             else               System out println  Odd    val

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Here s an example to determine whether a given number is even or odd   import java util Scanner   public class EvenOdd      public static void main String   args             int a        System out println  Please enter a number to check even or odd           Scanner sc   new Scanner System in         a   sc nextInt           if a   2    0                   System out println  Entered number is an even number                  else                  System out println  Entered number is an odd number                     Well  there are many ways to determine the same  Refer this resource for more examples to find the given number is even or odd

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if  x 2   0        even else       odd

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If the modulus of the given number is equal to zero  the number is even else odd number  Below is the method that does that   public void evenOrOddNumber int number      if  number   2    0        System out println  Number is Even         else       System out println  Number is odd

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I would recommend      Java Puzzlers  Traps  Pitfalls  and Corner Cases Book by Joshua Bloch   and Neal Gafter   There is a briefly explanation how to check if number is odd  First try is something similar what  AseemYadav tried   public static boolean isOdd int i         return i   2    1      but as was mentioned in book       when the remainder operation returns a nonzero result  it has the same   sign as its left operand   so generally when we have negative odd number then instead of 1 we ll get -1 as result of i 2  So we can use  Camilo solution or just do   public static boolean isOdd int i         return i   2    0      but generally the fastest solution is using AND operator like  lucasmo write above   public static boolean isOdd int i         return  i  amp  1     0       Edit It also worth to point Math floorMod int x  int y   which deals good with negative the dividend but also can return -1 if the divisor is negative

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Another easy way to do it without using if else condition  works for both positive and negative numbers    int n   8  List lt String gt  messages   Arrays asList  even    odd     System out println messages get Math abs n 2       For an Odd no   the expression will return  1  as remainder  giving     messages get 1     odd  and hence printing  odd    else   even  is printed when the expression comes up with result  0

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You can do like this   boolean is odd int n        return n   2    1    n   2    -1      This is because Java has in its modulo operation the sign of the dividend  the left side  n  So for negatives and positives dividends  the modulo has the sign of them   Of course  the bitwise operation is faster and optimized  simply document the line of code with two or three short words  which does it for readability

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Here is full example -  import java text ParseException   public class TestOddEvenExample       public static void main String args    throws ParseException            int x   24          oddEvenChecker x            int xx   3          oddEvenChecker xx              static void oddEvenChecker int x            if  x   2    0              System out println  You entered an even number     x           else             System out println  You entered an odd number     x

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This following program can handle large numbers   number of digits greater than 20    package com isEven java  import java util Scanner   public class isEvenValuate   public static void main String   args                         Scanner in   new Scanner System in           String digit   in next             int y   Character getNumericValue digit charAt digit length  -1             boolean isEven    y amp 1   0           if isEven              System out println  Even            else             System out println  Odd               Here is the output       122873215981652362153862153872138721637272   Even

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The remainder operator     will give you the remainder after dividing by a number   So n   2    0 will be true if n is even and false if n is odd

[java] Check whether number is even or odd

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