How to add an element at the end of an array

Question

I want to know how to add or append a new element to the end of an array  Is any simple way to add the element at the end  I know how to use a StringBuffer but I don t know how to use it to add an element in an array  I prefer it without an ArrayList or list   I wonder if the StringBuffer will work on integers

User · Answer

To clarify the terminology right  arrays are fixed length structures  and the length of an existing cannot be altered  the expression add at the end is meaningless  by itself    What you can do is create a new array one element larger and fill in the new element in the last slot   public static int   append int   array  int value         int   result   Arrays copyOf array  array length   1        result result length - 1    value       return result      This quickly gets inefficient  as each time append is called a new array is created and the old array contents is copied over   One way to drastically reduce the overhead is to create a larger array and keep track of up to which index it is actually filled  Adding an element becomes as simple a filling the next index and incrementing the index  If the array fills up completely  a new array is created with more free space   And guess what ArrayList does  exactly that  So when a dynamically sized array is needed  ArrayList is a good choice  Don t reinvent the wheel

User · Answer

one-liner with streams  Stream concat Arrays stream  array    Stream of  newElement    toArray

User · Answer

As many others pointed out if you are trying to add a new element at the end of list then something like  array array length-1  x  should do  But this will replace the existing element   For something like continuous addition to the array  You can keep track of the index and go on adding elements till you reach end and have the function that does the addition return you the next index  which in turn will tell you how many more elements can fit in the array   Of course in both the cases the size of array will be predefined  Vector can be your other option since you do not want arraylist  which will allow you all the same features and functions and additionally will take care of incrementing the size   Coming to the part where you want StringBuffer to array  I believe what you are looking for is the getChars int srcBegin  int srcEnd char   dst int dstBegin  method  Look into it that might solve your doubts  Again I would like to point out that after managing to get an array out of it  you can still only replace the last existing element character in this case

User · Answer

Arrays in Java have a fixed length that cannot be changed  So Java provides classes that allow you to maintain lists of variable length   Generally  there is the List lt T gt  interface  which represents a list of instances of the class T  The easiest and most widely used implementation is the ArrayList  Here is an example   List lt String gt  words   new ArrayList lt String gt     words add  Hello    words add  World    words add         List add   simply appends an element to the list and you can get the size of a list using List size

User · Answer

You can not add an element to an array  since arrays  in Java  are fixed-length  However  you could build a new array from the existing one using Arrays copyOf array  size     public static void main String   args        int   array   new int    1  2  3       System out println Arrays toString array        array   Arrays copyOf array  array length   1     create new array from old array and allocate one more element     array array length - 1    4      System out println Arrays toString array        I would still recommend to drop working with an array and use a List

User · Answer

The OP says  for unknown reasons   I prefer it without an arraylist or list    If the type you are referring to is a primitive  you mention integers  but you don t say if you mean int or Integer   then you can use one of the NIO Buffer classes like java nio IntBuffer  These act a lot like StringBuffer does - they act as buffers for a list of the primitive type  buffers exist for all the primitives but not for Objects   and you can wrap a buffer around an array and or extract an array from a buffer   Note that the javadocs say   The capacity of a buffer is never negative and never changes   It s still just a wrapper around an array  but one that s nicer to work with  The only way to effectively expand a buffer is to allocate   a larger one and use put   to dump the old buffer into the new one   If it s not a primitive  you should probably just use List  or come up with a compelling reason why you can t or won t  and maybe somebody will help you work around it

[java] How to add an element at the end of an array?

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