Why isn't there a java.lang.Array class? If a java array is an Object, shouldn't it extend Object?

Question

Here is the java package-tree: http://docs.oracle.com/javase/7/docs/api/java/lang/package-tree.html

I read a tutorial on Java which stated that in Java arrays are objects.

Where is the array class? How comes we can make arrays like this:

byte[] byteArr = new byte[]; char[] charArr = new char[]; int[] intArr = new int[]; 

and the arrays will inherit methods from Object; for example:

    byte thisByte = 1;     byte thatByte = 2;     byte[] theseBytes = new byte[] {thisByte, thatByte};     int inheritance = theseBytes.length; //inherited 'length' field and some methods     int wasntInWill = thatByte.length; //error 

What's going on here?

EDIT:

As per the answers, I now know it is a final class in java.lang.reflect package.

I have now created a package java.lang.reflect in my Android project and have added a class called Array.java to it. To confirm this is in the way of the original class, Eclipse gave me the error "... already exists in path/to/android.jar"

If I write out the same class as java.lang.reflect.Array but change the toString() method... this should work within my application right?

Answer 1

From JLS:

Every array has an associated Class object, shared with all other arrays with the same component type. [This] acts as if: the direct superclass of an array type is Object [and] every array type implements the interfaces Cloneable and java.io.Serializable.

This is shown by the following example code:

class Test {     public static void main(String[] args) {         int[] ia = new int[3];         System.out.println(ia.getClass());         System.out.println(ia.getClass().getSuperclass());     } } 

which prints:

class [I class java.lang.Object 

where the string "[I" is the run-time type signature for the class object "array with component type int".

And yes, since array types effectively extend Object, you can invoke toString() on arrayObject also see the above example

int arr[] = new arr[2]; arr.toString();