How to add an element at the end of an array?

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.

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<T> 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<String> words = new ArrayList<String>();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().

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.