How can we dynamically allocate and grow an array

Question

I am working on a project, but I cannot use any existing java data structures (ie, ArraysList, trees, etc)

I can only use arrays. Therefore, I need to dynamically up

Answer 1

you can not increase array size dynamically better you copy into new array. Use System.arrayCopy for that, it better than copying each element into new array. For reference Why is System.arraycopy native in Java?.

private static Object resizeArray (Object oldArray, int newSize) {
   int oldSize = java.lang.reflect.Array.getLength(oldArray);
   Class elementType = oldArray.getClass().getComponentType();
   Object newArray = java.lang.reflect.Array.newInstance(
         elementType, newSize);
   int preserveLength = Math.min(oldSize, newSize);
   if (preserveLength > 0)
      System.arraycopy(oldArray, 0, newArray, 0, preserveLength);
   return newArray;
}