Preserving 2D Array Modifications with Duplication

In Java, when creating copies of objects, it's crucial to understand the reference assignment behavior. In the given scenario, two 2D arrays named current and old are defined, along with methods to copy the contents.

The old() method assigns the current array to old. However, this merely transfers the reference to the same array in memory. When updates are made to current, old also reflects these changes, since they both point to the same underlying array.

The keepold() method attempts to assign the old array to current. Again, this only updates the reference, leaving the original current array unaffected. As a result, when updates are made to current, the contents of old remain unchanged.

To create a true copy of a 2D array in Java, it's necessary to manually copy each element. Alternatively, for more efficient copying, you can utilize the Arrays.stream().map()...toArray() method, which employs the streams API to create a clone of each row and assemble them into a new array.