What condition prohibits inserting new elements into the array?

In Java, arrays have a fixed size, which is set when they are created. This means that after initializing an array, you cannot add new elements to it unless you create a new array of a larger size and copy the data into it.

Therefore, the condition that prohibits adding new elements to an array is the fixed size of the array, determined at its creation.

Example:

int[] arr = new int[5]; // array of size 5
arr[0] = 10; // you can assign a value to an existing index
// arr[5] = 20; // compilation error: index out of bounds
// You cannot add a 6th element, as the size is fixed