mock question Wrapper issue

[Youssef Ghazal]

Hello

i try it one mock exam and i stopped in this question :

What will happen if you attempt to compile and run the following code?

  
Integer ten=new Integer(10);
Long nine=new Long (9);
System.out.println(ten + nine);
int i=1;
System.out.println(i + ten);
  

1) 19 followed by 20
2) 19 followed by 11
3) Compile time error
4) 10 followed by 1

and i choose the second option ,and i confirmed my option with running the code and it showed "19 10"

but when i see them answer i was suprised they said a compile error will occurs

The wrapper classes cannot be used like primitives.

Depending on your compiler you will get an error that says someting like "Error: Can't convert java lang Integer". Wrapper classes have similar names to primitives but all start with upper case letters.

Thus in this case we have int as a primitive and Integer as a wrapper. The objectives do not specifically mention the wrapper classes but don't be surprised if they come up.

.i don't see why .
[ August 26, 2007: Message edited by: Youssef Ghazal ]

[Ajay Divakaran]

i got the o/p as
19 11

[Jesper de Jong]

Autoboxing (automatically converting primitive types to instances of wrapper classes) is a new feature of Java 5.

Was the mock exam you are doing for Java 1.4?

[Youssef Ghazal]

yes,
it's a java 4 version.
thanks