Any shortcut to initialize all array elements to zero

Question

In C C   I used to do   int arr 10     0        to initialize all my array elements to 0   Is there a similar shortcut in Java   I want to avoid using the loop  is it possible   int arr     new int 10   for int i   0  i  lt  arr length  i          arr i    0

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If you are using Float or Integer then you can assign default value like this      Integer   data   new Integer 20   Arrays fill data new Integer 0

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Yet another approach by using lambda above java 8   Arrays stream new Integer nodelist size     map e - gt    Integer MAX VALUE  toArray Integer    new

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While the other answers are correct  int array values are by default initialized to 0   if you wanted to explicitly do so  say for example if you wanted an array filled with the value 42   you can use the fill   method of the Arrays class   int    myarray   new int num elts   Arrays fill myarray  42     Or if you re a fan of 1-liners  you can use the Collections nCopies   routine   Integer   arr   Collections nCopies 3  42  toArray new Integer 0      Would give arr the value    42  42  42     though it s Integer  and not int  if you need the primitive type you could defer to the Apache Commons ArrayUtils toPrimitive   routine   int    primarr   ArrayUtils toPrimitive arr

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The int values are already zero after initialization  as everyone has mentioned  If you have a situation where you actually do need to set array values to zero and want to optimize that  use System arraycopy   static private int   zeros   new float 64       int   values       if  zeros length  lt  values length  zeros   new int values length   System arraycopy zeros  0  values  0  values length     This uses memcpy under the covers in most or all JRE implementations  Note the use of a static like this is safe even with multiple threads  since the worst case is multiple threads reallocate zeros concurrently  which doesn t hurt anything   You could also use Arrays fill as some others have mentioned  Arrays fill could use memcpy in a smart JVM  but is probably just a Java loop and the bounds checking that entails   Benchmark your optimizations  of course

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Initialization is not require in case of zero because default value of int in Java is zero  For values other than zero java util Arrays provides a number of options  simplest one is fill method   int   arr   new int 5   Arrays fill arr  -1   System out println Arrays toString arr        -1  -1  -1  -1  -1    int    arr   new int 5      fill value 1 from index 0  inclusive  to index 3  exclusive Arrays fill arr  0  3  -1   System out println Arrays toString arr        -1  -1  -1  0  0    We can also use Arrays setAll   if we want to fill value on condition basis   int   array   new int 20   Arrays setAll array  p - gt  p  gt  10   -1   p    int   arr   new int 5   Arrays setAll arr  i - gt  i   System out println Arrays toString arr          0  1  2  3  4

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declare the array as instance variable in the class i e  out of every method and JVM will give it 0 as default value  You need not to worry anymore

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Yes  int values in an array are initialized to zero  But you are not guaranteed this  Oracle documentation states that this is a bad coding practice

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How it Reduces the Performance of your application      Read Following   In Java Language Specification the Default   Initial Value for any Object can be given as Follows   For type byte  the default value is zero  that is  the value of  byte  is 0   For type short  the default value is zero  that is  the value of  short  is 0   For type int  the default value is zero  that is  0   For type long  the default value is zero  that is  0L   For type float  the default value is positive zero  that is  0 0f   For type double  the default value is positive zero  that is  0 0d   For type char  the default value is the null character  that is    u0000    For type boolean  the default value is false   For all reference types  the default value is null   By Considering all this you don t need to initialize with zero values for the array elements because by default all array elements are 0 for int array   Because An array is a container object that holds a fixed number of values of a single type   Now the Type of array for you is int so consider the default value for all array elements will be automatically 0 Because it is holding int type   Now consider the array for String type so that all array elements has default value is null   Why don t do that         you can assign null value by using loop as you suggest in your Question   int arr     new int 10   for int i 0 i lt arr length i        arr i    0    But if you do so then it will an useless loss of machine cycle  and if you use in your application where you have many arrays and you do that for each array then it will affect the Application Performance up-to considerable level   The more use of machine cycle     More time to Process the data     Output time will be significantly increase  so that your application data processing can be considered as a low level Slow up-to some Level

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In c cpp there is no shortcut but to initialize all the arrays with the zero subscript Ex     int arr 10     0     But in java there is a magic tool called Arrays fill   which will fill all the values in an array with the integer of your choice Ex     import java util Arrays       public class Main             public static void main String   args                    int ar      2  2  1  8  3  2  2  4  2            Arrays fill ar  10            System out println  Array completely filled                                            with 10 n    Arrays toString ar

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You can create a new empty array with your existing array size  and you can assign back them to your array  This may faster than other  Snipet    package com array zero  public class ArrayZero   public static void main String   args           Your array with data     int   yourArray     1  2  3  4  5  6  7  8  9          Creating same sized array with 0     int   tempArray   new int yourArray length       Assigning temp array to replace values by zero  0      yourArray   tempArray         testing the array size and value to be zero     for  int item   yourArray            System out println item               Result    0 0 0 0 0     0 0 0 0

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A default value of 0 for arrays of integral types is guaranteed by the language spec      Each class variable  instance variable  or array component is initialized with a default value when it is created    15 9    15 10        For type int  the default value is zero  that is  0   nbsp    If you want to initialize an one-dimensional array to a different value  you can use java util Arrays fill    which will of course use a loop internally

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In java all elements primitive integer types byte short  int  long  are initialised to 0 by default  You can save the loop

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You can save the loop  initialization is already made to 0  Even for a local variable   But please correct the place where you place the brackets  for readability  recognized best-practice    int   arr   new int 10

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int a 7  b 7  c 0 d 0      int dizi     new int a  b       for int i 0 i lt a i             for int q d q lt b q                 dizi i  q  c                             System out print dizi i  q                c                       c- b 1          System out println                           result      0123456     -1012345     -2-101234     -3-2-10123     -4-3-2-1012     -5-4-3-2-101     -6-5-4-3-2-10

[java] Any shortcut to initialize all array elements to zero?

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