How do you find the sum of all the numbers in an array in Java

Question

I m having a problem finding the sum of all of the integers in an array in Java  I cannot find any useful method in the Math class for this

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public class AddDemo        public static void main String   args             ArrayList  lt Integer gt A   new ArrayList lt Integer gt              Scanner S   new Scanner System in            System out println  Enter the Numbers               for int i 0  i lt 5  i                  A add S nextInt                        System out println  You have entered    A            int Sum   0           for int i 0  i lt A size    i                  Sum   Sum   A get i                       System out println  The Sum of Entered List is    Sum

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You can make your code look better like this   public void someMethod        List lt Integer gt  numbers   new ArrayList lt Integer gt         numbers addAll db findNumbers                 System out println  Result is     sumOfNumbers numbers       private int sumOfNumbers List lt Integer gt  numbers       int sum   0      for  Integer i   numbers         sum    i            return sum

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Most of the answers here are using inbuilt functions- Here is my answer if you want to know the whole logic behind this ques  import java util     public class SumOfArray       public static void main String   args           Scanner inp   new Scanner System in           int n   inp nextInt            int   arr   new int n           for int i   0  i  lt  n  i                 arr i    inp nextInt                      System out println  quot The sum of the array is   quot    sum arr              static int sum int   arr           int sum   0          for  int a   0  a  lt  arr length  a                 sum   sum   arr a                     return sum

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Sum of all elements from 1 to 1000     final int sum   Stream iterate 1  n - gt  n   1  limit 1000  mapToInt el - gt  el  sum

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In java-8 you can use streams   int   a    10 20 30 40 50   int sum   IntStream of a  sum    System out println  The sum is     sum     Output   The sum is 150   It s in the package java util stream  import java util stream

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class Addition         public static void main               int arr    5 10 15 20 25 30             Declaration and Initialization of an Array           int sum 0                               To find the sum of array elements           for int i arr                  sum    i                        System out println  The sum is    sum    To display the sum

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I like this method personally  My code style is a little weird   public static int sumOf int    integers        int total   0      for  int i   0  i  lt  integers length  total    integers i          return total      Pretty easy to use in code   int   numbers     1  2  3  4  5    sumOf 1   sumOf 1  2  3   sumOf numbers

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There is no  method in a math class  for such thing  Its not like its a square root function or something like that   You just need to have a variable for the sum and loop through the array adding each value you find to the sum

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If you re using Java 8  the Arrays class provides a stream int   array  method which returns a sequential IntStream with the specified int array  It has also been overloaded  for double and long arrays   int    arr    1 2 3 4   int sum   Arrays stream arr  sum      prints 10   It also provides a method  stream int   array  int startInclusive  int endExclusive  which permits you to take a specified range of the array  which can be useful     int sum   Arrays stream new int    1 2 3 4   0  2  sum      prints 3   Finally  it can take an array of type T  So you can per example have a String which contains numbers as an input and if you want to sum them just do    int sum   Arrays stream  1 2 3 4  split    s     mapToInt Integer  parseInt  sum

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public class Num1         public static void main                       Declaration and Initialization           int a    10 20 30 40 50               To find the sum of array elements           int sum 0            for int i 0 i lt a length i                              sum sum i                           To display the sum           System out println  The sum is    sum

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There is a sum   method in underscore-java library   Code example   import com github underscore lodash U   public class Main       public static void main String   args            int sum   U sum java util Arrays asList 1  2  3  4             System out println sum              - gt  10

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As of Java 8 The use of lambda expressions have become available   See this    int   nums       Your Array        Compact    int sum   0  Arrays asList nums  stream   forEach each - gt        sum    each        Prefer    int sum   0   ArrayList lt Integer gt  list   new ArrayList lt Integer gt      for  int each   nums      refer back to original array      list add each     there are faster operations       list stream   forEach each - gt        sum    each        Return or print sum

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We may use user defined function  At first initialize sum variable equal to zero  Then traverse the array and add element with sum   Then update the sum variable   Code Snippet      import java util       import java lang      import java io      class Sum       public static int sum int arr                  int sum 0           for int i 0  i lt arr length  i                          sum    arr i                     return sum             public static void main  String   args                  int arr      1  2  3  4  5              int total   sum arr              System out printf   d   total

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int sum   0   for  int i   0  i  lt  yourArray length  i        sum   sum   yourArray i

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There are two things to learn from this exercise    You need to iterate through the elements of the array somehow - you can do this with a for loop or a while loop  You need to store the result of the summation in an accumulator   For this  you need to create a variable   int accumulator   0  for int i   0  i  lt  myArray length  i          accumulator    myArray i

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The only point I would add to previous solutions is that I would use a long to accumulate the total to avoid any overflow of value   int   someArray    1  2  3  4  5  6  7  8  9  10  Integer MAX VALUE   long sum   0   for  int i   someArray      sum    i

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You have to roll your own  You start with a total of 0  Then you consider for every integer in the array  add it to a total  Then when you re out of integers  you have the sum   If there were no integers  then the total is 0

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int sum   0  for  int i   0  i  lt  myArray length  i      sum    myArray i

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In Java 8   Code      int   array   new int   1 2 3 4 5      int sum   IntStream of array  reduce  0  a  b  - gt  a   b      System out println  The summation of array is     sum      System out println  Another way to find summation      IntStream of array  sum       Output   The summation of array is 15 Another way to find summation  15   Explanation   In Java 8  you can use reduction concept to do your addition   Read all about Reduction

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Use below logic   static int sum                   int sum   0     initialize sum          int i               Iterate through all elements summing them up          for  i   0  i  lt  arr length  i                sum     arr i             return sum

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I use this   public static long sum int   i arr        long sum      int i      for sum  0  i  i arr length - 1  0  lt   i  sum   i arr i--        return sum

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A bit surprised to see None of the above answers considers it can be multiple times faster using a thread pool  Here  parallel uses a fork-join thread pool and automatically break the stream in multiple parts and run them parallel and then merge  If you just remember the following line of code you can use it many places      So the award for the fastest short and sweet code goes to -   int   nums    1 2 3   int sum    Arrays stream nums  parallel   reduce 0   a b - gt  a b     Lets say you want to do sum of squares   then Arrays stream nums  parallel   map x- x x  reduce 0   a b -  a b   Idea is you can still perform reduce   without map

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IMHO a sum function would seem a good fit to extend the Arrays class where fill  sort  search  copy   amp  equals live  There are a lot of handy methods hiding in the javadocs so it is a fair question when porting Fortran to java to ask before rolling our own helper method  Search through the huge javadoc index for  sum    add  and any other keyword you might think of  You might suspect certainly someone has already done this for primitive types int  float  double  Integer  Float  Double  No matter how simple  it is always good to check  Keep the code as simple as possible and don t reinvent the wheel

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It depends  How many numbers are you adding  Testing many of the above suggestions   import java text NumberFormat  import java util Arrays  import java util Locale   public class Main        public static final NumberFormat FORMAT   NumberFormat getInstance Locale US        public static long sumParallel int   array            final long start   System nanoTime            int sum   Arrays stream array  parallel   reduce 0  a b - gt   a   b           final long end   System nanoTime            System out println sum           return  end - start             public static long sumStream int   array            final long start   System nanoTime            int sum   Arrays stream array  reduce 0  a b - gt   a   b           final long end   System nanoTime            System out println sum           return  end - start             public static long sumLoop int   array            final long start   System nanoTime            int sum   0          for  int v  array                sum    v                    final long end   System nanoTime            System out println sum           return  end - start             public static long sumArray int   array            final long start   System nanoTime            int sum   Arrays stream array   sum            final long end   System nanoTime            System out println sum           return  end - start             public static long sumStat int   array            final long start   System nanoTime            int sum   0          final long end   System nanoTime            System out println sum           return  end - start              public static void test int   nums            System out println  ------            System out println FORMAT format nums length      numbers            long p   sumParallel nums           System out println  parallel     FORMAT format p            long s   sumStream nums           System out println  stream      FORMAT format s            long ar   sumArray nums           System out println  arrays      FORMAT format ar            long lp   sumLoop nums           System out println  loop      FORMAT format lp                public static void testNumbers int howmany            int   nums   new int howmany           for  int i  0  i  lt  nums length i                  nums i     i   1  100                    test nums              public static void main String   args            testNumbers 3           testNumbers 300           testNumbers 3000           testNumbers 30000           testNumbers 300000           testNumbers 3000000           testNumbers 30000000           testNumbers 300000000             I found  using an 8 core  16 G Ubuntu18 machine  the loop was fastest for smaller values and the parallel for larger  But of course it would depend on the hardware you re running   ------ 3 numbers 6 parallel 4 575 234 6 stream 209 849 6 arrays 251 173 6 loop 576 ------ 300 numbers 14850 parallel 671 428 14850 stream 73 469 14850 arrays 71 207 14850 loop 4 958 ------ 3 000 numbers 148500 parallel 393 112 148500 stream 306 240 148500 arrays 335 795 148500 loop 47 804 ------ 30 000 numbers 1485000 parallel 794 223 1485000 stream 1 046 927 1485000 arrays 366 400 1485000 loop 459 456 ------ 300 000 numbers 14850000 parallel 4 715 590 14850000 stream 1 369 509 14850000 arrays 1 296 287 14850000 loop 1 327 592 ------ 3 000 000 numbers 148500000 parallel 3 996 803 148500000 stream 13 426 933 148500000 arrays 13 228 364 148500000 loop 1 137 424 ------ 30 000 000 numbers 1485000000 parallel 32 894 414 1485000000 stream 131 924 691 1485000000 arrays 131 689 921 1485000000 loop 9 607 527 ------ 300 000 000 numbers 1965098112 parallel 338 552 816 1965098112 stream 1 318 649 742 1965098112 arrays 1 308 043 340 1965098112 loop 98 986 436

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In Apache Math   There is StatUtils sum double   arr

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You can t  Other languages have some methods for this like array sum   in PHP  but Java doesn t   Just    int   numbers    1 2 3 4   int sum   0  for  int i   numbers        sum    i     System out println sum

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This is one of those simple things that doesn t  AFAIK  exist in the standard Java API  It s easy enough to write your own   Other answers are perfectly fine  but here s one with some for-each syntactic sugar   int someArray      1  2  3  4  5  6  7  8  9  10   int sum   0   for  int i   someArray      sum    i    Also  an example of array summation is even shown in the Java 7 Language Specification  The example is from Section 10 4 - Array Access   class Gauss       public static void main String   args            int   ia   new int 101           for  int i   0  i  lt  ia length  i    ia i    i          int sum   0          for  int e   ia  sum    e          System out println sum

[java] How do you find the sum of all the numbers in an array in Java?

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