I want to declare an empty array in java and then I want do update it but the code is not working

Question

I want to declare an empty array in java and then I want do update it but the code is not working     public class JavaConversion       public static void main String args                  int array               int number   5  i   0 j   0          while  i lt 4                array i  number              i i 1                    while  j lt 4                System out println array j

User · Answer

Your code compiles just fine  However  your array initialization line is wrong    int array         What this does is declare an array with a size equal to the number of elements in the brackets  Since there is nothing in the brackets  you re saying the size of the array is 0 - this renders the array completely useless  since now it can t store anything    Instead  you can either initialize the array right in your original line    int array       5  5  5  5      Or you can declare the size and then populate it    int array     new int 4         while loop   If you don t know the size of the array ahead of time  for example  if you re reading a file and storing the contents   you should use an ArrayList instead  because that s an array that grows in size dynamically as more elements are added to it  in layman s terms

User · Answer

You can t set a number in an arbitrary place in the array without telling the array how big it needs to be  For your example  int   array   new int 4

User · Answer

You need to give the array a size   public static void main String args          int array     new int 4       int number   5  i   0 j   0      while  i lt 4           array i  number          i i 1            while  j lt 4           System out println array j            j

User · Answer

You are creating an array of zero length  no slots to put anything in   int array      nothing in here   array with no elements      and then trying to assign values to array elements  which you don t have  because there are no slots  array i    number    array i    element i in the array of length 0  You need to define a larger array to fit your needs  int array     new int 4     Create an array with 4 elements  0   1   2  and  3  each containing an int value

User · Answer

You can do some thing like this   Initialize with empty array and assign the values later  String importRt    23 43 43 34   if null    importRt                importArray   Arrays stream importRt split                            map String  trim                       toArray String    new              System out println Arrays toString exportImportArray      Hope it helps

User · Answer

So the issue is in your array declaration you are declaring an empty array with the empty curly braces   instead of an array that allows slots  Roughly speaking  there can be three types of inputs     1  int array     null   Does not point to any memory locations so is a null arrau  2  int array        which is sort of equivalent to int array     new int 0    3  int array     new int n  where n is some number indicating the number of  memory locations in the array

[java] I want to declare an empty array in java and then I want do update it but the code is not working

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