Dan's exam

[Sagarika nair]

Hello friends!
I have a doubt about an answer explanation in Dan's site.For the question number 12.
1)A single local variable declaration statement may contain a comma separated list of variable declarators: "int i=0, j=0;".
2)Alternatively, the same two variables could be declared using two local variable declaration statements: "int i=0; int j=0;". Please note that the two statements are separated by a semicolon, and each declares the type of the variable
DanChisholm
The point no.1 is fine but the point no 2 stating that int i=0;int j=0; is what I am not clear about coz when I tried it, it gives a compiler error but Dan states that it is an alternate way to declare in a for loop.
for(int i=0;int j=0;i<2;i++,j++)
According to me the above for loop stmt gives an error.
The only correct way should be
for(int i=0,j=0;i<2;i++,j++)
Am I right?
Please help.
Thanks.
Sagarika

[mrudul joshi]

Hi,
Yes, I think you are right. The structure of the loop is,
for(initialization; boolean expression;step statement)and we can have as many initialization and step portions as we want to have provoded that they are separated by a comma.
For example,
for(int i =0, int j=12;j<12;i++)

[Dan Chisholm]

The question is as follows.

class JMM124 {
  public static void main(String args[]) {
    int k;
    for (int i=0, j=0; i<2; i++,j++) {System.out.print(i);}     // 1
    for (int i=0, k=0; i<2; i++,k++) {System.out.print(i);}     // 2
    for (int i=0, int j=0; i<2; i++,j++) {System.out.print(i);} // 3
}}
What is the result of attempting to compile and run the program? 
a.  Prints: 012345 
b.  Prints: 010101 
c.  Compile-time error at line 1 
d.  Compile-time error at line 2 
e.  Compile-time error at line 3 
f.  Run-time error 

The Answers are d and e.
The explanation is as follows.

A compile-time error occurs at line 2 as a result of the attempt to shadow the method local variable, k, within the for-loop. A variable declared within the for-loop can not shadow a local variable of the enclosing method. At line 3, the declaration of variable j causes a compile-time error. A single local variable declaration statement may contain a comma separated list of variable declarators: "int i=0, j=0;". Alternatively, the same two variables could be declared using two local variable declaration statements: "int i=0; int j=0;". Please note that the two statements are separated by a semicolon, and each declares the type of the variable. The initialization part of a for statement may use a single local variable declaration statement to declare more than one local variable. Each of the new variables is declared in a comma separated list of variable declarators. In this program, the local variables should have been declared as follows: "int i=0, j=0;". Instead, the type of variable j has been incorrectly added to the declarator: "int i=0, int j=0;". The result is a compile-time error.

The key sentence in this explanation is the following.

The initialization part of a for statement may use a single local variable declaration statement to declare more than one local variable. Each of the new variables is declared in a comma separated list of variable declarators.

The sentences that you have quoted are as follows.

A single local variable declaration statement may contain a comma separated list of variable declarators: "int i=0, j=0;". Alternatively, the same two variables could be declared using two local variable declaration statements: "int i=0; int j=0;".

Those statements were not intended to refer to the initialization part of a for statement. Instead, they were intended to describe alternative forms of declarations of local variables. After reading your comments, I can see that the intent of the above quote is not clear. I now see that the entire explanation would be more clear if I just delete the confusing sentences. The next version of the exam will not contain those sentences.
Thank you for using my exam, and thank you for the feedback.