Chapter 6 from K&B question 12

[kirba devi]

Hi ,
i have created a folder Cdir,created two subdirectories dir1,dir2 and placed file1.txt,file2.txt accordingly as per question no 12.

for those who not having book.

 and that the invocation
java Directories file2.txt
is issued from a directory that has two subdirectories, "dir1" and "dir1", and that "dir1" has a
file "file1.txt" and "dir2" has a file "file2.txt", and the output is "false true", which
set(s) of code fragments must be inserted? (Choose all that apply.)
A. String path = d;
System.out.print(file.exists() + " ");
B. String path = d;
System.out.print(file.isFile() + " ");
C. String path = File.separator + d;
System.out.print(file.exists() + " ");
D. String path = File.separator + d;
System.out.print(file.isFile() + " ");
and that the invocation
java Directories file2.txt
is issued from a directory that has two subdirectories, "dir1" and "dir1", and that "dir1" has a
file "file1.txt" and "dir2" has a file "file2.txt", and the output is "false true", which
set(s) of code fragments must be inserted? (Choose all that apply.)
A. String path = d;
System.out.print(file.exists() + " ");
B. String path = d;
System.out.print(file.isFile() + " ");
C. String path = File.separator + d;
System.out.print(file.exists() + " ");
D. String path = File.separator + d;
System.out.print(file.isFile() + " "); 

answers:A,B

Compiled it proper for the first iteration path=dir1 arg[0]=file2.txt
file.exists is false thatis okie as there is no such file in that dir1.
but for the second iteration of for loop path=dir2 arg[0]=file2.txt i am getting false,this i cannot beleive as file2.txt is there in dir2?
also i need information why option c,d is wrong?


Regards
Kirba.

[kirba devi]

i forgot to add the code properly.

import java.io.*;
class Directories {
static String [] dirs = {"dir1", "dir2"};
public static void main(String [] args) {
for (String d : dirs) {
// insert code 1 here
File file = new File(path, args[0]);
// insert code 2 here
}
}
}

[Santhosh Kumar]

Answers C and D are wrong because, prefixing File.separator adds "/" (in unix) or "\" (in windows) to the means path is absolute one starts the the root of the file system, which doesn't have "dir1" and "dir2" in this case.

Paths can be referred in the File object in two ways. Relative and Absolute. If the path string starts with "/" or "\", then it is considered as absolute otherwise, relative.

In case of relative path string, the File object takes the current working directory (user.dir system variable) of the application and prefixes to the path string.

So make sure you are running the application from the CDir otherwise, Java app won't see the dir1 and dir2 folders.