Wrapper class

[Pawan Arora]

The question been taken from kathy sierra and bert bates chapter book, and the question is
1. class Convert {
2. public static void main(String[] args) {
3. Long xL = new Long(456L);
4. long x1 = Long.valueOf("123");
5. Long x2 = Long.valueOf("123");
6. long x3 = xL.longValue();
7. Long x4 = xL.longValue();
8. Long x5 = Long.parseLong("456");
9. long x6 = Long.parseLong("123");
10. }
11. }
Which will compile using Java 5, but will NOT compile using Java 1.4? (Choose all that apply.)
A. Line 4.
B. Line 5.
C. Line 6.
D. Line 7.
E. Line 8.
F. Line 9.
I think the answer is A,B,C,D

[Paul Campbell]

a, d, e

[Pawan Arora]

Originally posted by Paul Campbell:
a, d, e

do you have any reason?

[subhasish nag]

Because the feature Boxing & Autoboxing is not available below version 1.5

[Pawan Arora]

Originally posted by subhasish nag:
Because the feature Boxing & Autoboxing is not available below version 1.5

I know that autoboxing & Boxing is new 1.5. I just don't comprehend why the option A is correct and not option B so, because both are perofming the same work.

[Ridhav Mahajan]

This is bcozzz Long.valueof() returns Long, not primitive type long.
There i difference between long and Long in java.
Hence when you assign Long.valueof() to long, it require autoboxing which is available only in java 5 onwards.

[Ridhav Mahajan]

and in option B i.e line 5
we are getting Long and assigning it to Long; hence it doesnt require java 5, whereas if you asign it to long , then you require autoboxing feature

[Christophe Verré]

"Ridhav",
Welcome to the ranch. You may not be aware of the ranch Naming Policy. Please read it carefully and change your name accordingly (you need to set both first and last names). Thank you.