数组是 Java 中的对象吗？

Question

As we know that arrays are objects, so what is the class behind creation of array objects.

When we write a statement, int a[]=new int[56];

Here int is a primitive, it cannot be the class used for defining array objects,

Object can be the superclass of array objects, but it can't be the immediate class as it doesn't contain length field. So please help me in understanding this fact.

Answer 1

JLS §4.3.1 defines an object as :

[...] a class instance or an array.

" Object can be the superclass of array objects " - This is not quite correct. There is no explicit class for arrays and thus another class cannot extend an array. The element-type of an array is independent and can be either a primitive or an object.

As to the question how the length of an array works, the JLS defines it in §10.3 :

[...]

An array creation expression specifies the element type, the number of levels of nested arrays, and the length of the array for at least one of the levels of nesting. The array's length is available as a final instance variable length .

[...]

Answer 2

Arrays are builtin with Java itself, you can't find a class for it like you would for example String .

Arrays are Objects in java, that's true.

When we write a statement, int a[]=new int[56];

Here int is a primitive, it cannot be the class used for defining array objects...

int does represent primitive type values, but the object(array) is not of int type it just contains elements of type int .

can you tell me how arr.length works if we say arr is an object

Arrays ARE Objects as we already stated, length is a FIELD/ATTRIBUT E that every instance of array contains, that field is final and is created once you instantiate array:

int[] arrayOfInts = new int[ 23 ];

As you can see above we specify 23 for the size of our int[] and that size will be assigned to length field when our array is created, and we already said it's final so it can't be reassigned, we can only create new array not resize the current one.

Hope I cleared some of your confusion.

Answer 3

To put it in not-too-technical terms, arrays are a special kind of object. It's not an explicitly named class defined somewhere in the standard library like Map or String . It's more like something built into Java itself. It has its own special declaration syntax, but it behaves like all other objects.

Basically, for every primitive type or class defined, Java implicitly defines a corresponding array class that extends Object directly. It provides a special syntax for creating and accessing the array, but other than that, it is a plain object, with fields and overridden methods from Object , though those methods aren't really implemented to do anything useful.