How do you count the elements of an array in java

Question

Say i have the array  int theArray   new int 20     The length of the array is 20 but the count is 0  How can i get the count

User · Answer

If you assume that 0 is not a valid item in the array then the following code should work      public static void main  String   args              int   theArray   new int 20         theArray 0    1        theArray 1    2         System out println count theArray             private static int count int   array              int count   0        for int i   array                   if i  gt  0                         count                             return count

User · Answer

Java doesn t have the concept of a  count  of the used elements in an array   To get this  Java uses an ArrayList   The List is implemented on top of an array which gets resized whenever the JVM decides it s not big enough  or sometimes when it is too big      To get the count  you use mylist size   to ensure a capacity  the underlying array backing  you use mylist ensureCapacity 20    To get rid of the extra capacity  you use mylist trimToSize

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What do you mean by  the count   The number of elements with a non-zero value  You d just have to count them   There s no distinction between that array and one which has explicitly been set with zero values  For example  these arrays are indistinguishable   int   x     0  0  0    int   y   new int 3     Arrays in Java always have a fixed size - accessed via the length field  There s no concept of  the amount of the array currently in use

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Iterate through it and count the elements which aren t null   int counter   0  for  int i   0  i  lt  theArray length  i         if  theArray i     null          counter       This can be neatened up by using for each loops and suchlike  but this is the jist   Either that  or keep a counter and whenever you add an element  increment it

User · Answer

Your code won t compile  it should be int    theArray   new int 20    You can get the array length as theArray length  For primitive types  the array will be initialized with the default values  0 for int   You can make it Integer    theArray   new Integer 20   and then count initialized members as this code does   public int count Object    array        int c   0      for Object el  array    if el    null  c              return c       Please note that this answer isn t about why you may need this and what is the best way to do what you want

User · Answer

If you wish to have an Array in which you will not be allocating all of the elements  you will have to do your own bookkeeping to ensure how many elements you have placed in it via some other variable   If you d like to avoid doing this while also getting an  Array  that can grow capacities after its initial instantiation  you can create an ArrayList  ArrayList lt Integer gt  theArray   new ArrayList lt Integer gt     theArray add 5      places at index 0 theArray size       returns length of 1 int answer   theArray get 0      index 0   5   Don t forget to import it at the top of the file   import java util ArrayList

User · Answer

There is no built-in functionality for this  This count is in its whole user-specific  Maintain a counter or whatever

User · Answer

You can declare an array of booleans with the same length of your array   true  is used false  is not used  and change the value of the same cell number to true  Then you can count how many cells are used by using a for loop

User · Answer

You can use a for each loop and count the number of integer values that are significant  You could also use an ArrayList which will keep track of the couny for you  Everytime you add or remove objects from the list it will automatically update the count  Calling the size   method will give you the current number of elements

User · Answer

int theArray     new int 20   System out println theArray length

User · Answer

What I think you may want is an ArrayList lt Integer gt  instead of an array   This will allow you do to   ArrayList lt Integer gt  arr   new ArrayList lt Integer gt  20   System out println arr size       The output will be 0   Then  you can add things to the list  and it will keep track of the count for you    It will also grow the size of the backing storage as you need as well

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Isn t it just  System out println Array length    Because this is what it seems like you are looking for

User · Answer

When defining an array  you are setting aside a block of memory to hold all the items you want to have in the array   This will have a default value  depending on the type of the array member types   What you can t do is find out the number of items that you have populated  except for tracking it in your own code

[java] How do you count the elements of an array in java

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