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When learning to code in Java, one of the fundamental structures you'll encounter are arrays. An array is a container object that holds a fixed number of values of a single data type. This is crucial for maintaining order and predictability in your code.

Imagine an array as a series of lockers, with each locker designed to hold an item of a specific type. Just as you wouldn't store a backpack in a locker meant for a coat, you can't mix data types in an array meant for a single type like integers or strings. If you try to insert a different data type, you'll encounter an error, which aligns with the exercise statement a), making it false.

For example, an array declared as int[] numbers = new int[5]; can only contain integers. If you need to store different types in the same array, consider using an array of objects or other collection types in Java that allow for mixed types, such as ArrayList<Object>. Nevertheless, using collections that allow mixed types should be approached with caution, as it might make the code less predictable and harder to maintain.

Accessing the individual elements within an array is done through array indexing. Java arrays use zero-based indexing, which means the index of the first element is 0, the second is 1, and so on.

Let's suppose you have an array char[] letters = {'a', 'b', 'c', 'd', 'e'};. To access the third element ('c'), you use letters[2]. The number inside the brackets is the index. It's important to remember that this index must be an integer or an integer expression, which supports the explanation in step 2 deeming statement b) as false.

Array indices in Java are always integers—not floats, not strings, nor any other non-integer data type. Attempting to use a non-integer value as an array index will result in a compile-time error. Additionally, accessing an index outside the valid range of the array (e.g., letters[5] for our 5-element array) will throw an ArrayIndexOutOfBoundsException, signaling a critical error in your code.

The behavior of method calls in Java can seem perplexing at first, especially when dealing with array elements. Understanding whether the original data is affected when an array element is passed to a method, hinges on knowing about value types and reference types.

For primitive types (like int, double, or char), when you pass an element to a method, Java creates a copy of that value. Therefore, any changes made within the method do not affect the original element in the array, as described in step 3. This is called pass-by-value, which means you're safe to operate on the data without altering the original source, confirming the falseness of part of the statement c) regarding primitive types.

However, with reference types (such as objects), what gets passed to the method is a reference to the object, not a physical copy. Changes to the object's attributes via this reference, as detailed in step 4, do affect the original object stored in the array—the pass-by-reference concept. This understanding of method call behavior leads to the validity of the rest of statement c) for reference-type elements.

To ensure that you fully grasp this concept, consider running through a few test cases with both primitive and reference types. Pay close attention to whether the original data changes after a method call to drive home the distinct behaviors between primitive and reference types.