任何类型的 Java 数组在文件中实际上是什么样的？

Question

I'm learning about Java arrays and I read something along the lines of that Java arrays are actually objects. Does that mean that when I make an array, say int[] array = new int[10] , the underlying mechanism is really just a class file that gets created with 10 instance variables of type int that I can access with array[(0-9)]? If so, how does it do that and how does it work? And what is the conceptual reason (if any) for the syntax to declare arrays the way it is (so I can remember the syntax rules easier)?

This is what I read in the textbook I am learning from:

Creating and Accessing Arrays

In Java, an array is a special kind of object, but it is often more useful to think of an array as a collection of variables of the same type. For example, an array consisting of a collection of seven variables of type double can be created as follows:

 double[] temperature = new double[7];

This is like declaring the following seven strangely named variables to have the type double:

 temperature[0], temperature[1], temperature[2], temperature[3], temperature[4], temperature[5], temperature[6]

Answer 1

in the code where you allocate an array:

int myInts = new int[20];

The JVM will allocate a block the size of 20 times the size of an integer (4 bytes) in the heap. The array is accessed / indexed using the index offset times the primative object size (again in this case, 4 bytes)

Also, I believe that array indexing is built directly into Java byte codes.

--- Edit ---

On array indexing being built in: If you look here, you can confirm the aaload JBC command / retrieve from an array: https://en.wikipedia.org/wiki/Java_bytecode_instruction_listings

Answer 2

Arrays in Java are objects, but they are not instances of any class. There are no array classes -see On the object types - section 4.3.1 :

An object is a class instance or an array.

Array objects are similar to classes with a number of variables, but an array of 10 doubles is not a class. It's more like, "array of doubles" is one single type, and the number of instance variables is stored within the object itself, in the array's length field.

On arrays - section 10 :

In the Java programming language, arrays are objects (§4.3.1), are dynamically created, and may be assigned to variables of type Object (§4.3.2).

An array object contains a number of variables. The number of variables may be zero, in which case the array is said to be empty. The variables contained in an array have no names; instead they are referenced by array access expressions that use non-negative integer index values. These variables are called the components of the array.

How arrays are implemented in a JVM is another matter. In OpenJDK, the memory layout for array objects includes a pointer to an "ArrayKlass" which is an internal representation for the array type. The size of the array is included within the array object, and the array objects themselves can have an arbitrary size. This is different from objects that are class instances: class instances are always the same size.