About Question enthuware.ocajp.i.v7.2.1354 :

[javaman]

If I do this:
Object[] iA = new Object[10];
iA[0] = new Integer(1);
System.out.println(iA[0]);
I create a variable that points to an array that can hold 10 objects, assign an Integer to the 1st position and print that value:
run:
1
BUILD SUCCESSFUL (total time: 0 seconds)

Isn't this what the question asks - Which of the following correctly declare a variable which can hold an array of 10 integers??

[admin]

It is "integers" with small i (not capital I), which means you are dealing with primitives not wrapper objects. You cannot store primitive integers in an array of Objects.

HTH,
Paul.

[mrmuiz]

As the explanation says

Code: Select all

Object[] o = new int[10];

is not valid

but what about this?

Code: Select all

Object []t={1,2,3};

it's valid and compiles without any error. This is actually an array of integers stored in an array of Objects...
It's a bit confusing to me, but probably it's accepted because (maybe)

Code: Select all

Object []t={1,2,3};

is the same as

Code: Select all

		Object []t=new Object[10];
		t[0]=1;
		t[1]=2;
		t[2]=3;

where integers literals are atomatically wrapped into Integers objects before being added to the array. This would explain why

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		Object []t={1,2,3};
		System.out.println(t[0].getClass());

prints

Code: Select all

class java.lang.Integer

[mj.anjuthan]

As the explanation says

Code: Select all

Object[] o = new int[10];

is not valid
but what about this?

Code: Select all

Object []t={1,2,3};

it's valid and compiles without any error. This is actually an array of integers stored in an array of Objects...

In the case Object[] o = {1,2,3} the integer primitive values are autoboxed to Integer object and stored in the Object array o[];

Primitives values cannot be stored in Object array.

[jamesmccreary]

I find it interesting that the compiler treats
Object[] o = new int[3]
as invalid, whereas
Object[] o = new int{1,2,3}
as valid

Perhaps once we explicitly populate the array with actual integers (which become autoboxed into Integer wrapper classes), then everything is okay. Perhaps the compiler doesn't know in advance that you will populate the array with integer primitives (but what else would you do, you declared it as an int array!). I guess the compiler can only check one step at a time

[admin]

Object[] o = new int{1,2,3} is invalid.
Object[] o = new int[]{1,2,3} is invalid as well.
Neither will compile.

[Aayushma]

How will int[ ] iA and int iA[] point to 10 ints?

[admin]

How will int[ ] iA and int iA[] point to 10 ints?

iA will point to an array of 10 int elements. Like this:
iA = new int[10];