question about properties and command line arguements

[Brent W Farrell]

Hello all,
I am taking a sun practice exam for the scjp 5. Please help me with the following question:


1. class x {
2. public static void main(String [] args) {
3. String p = System.getProperty("x");
4. if(p.equals(args[1]))
5. System.out.println("found");
6. }
7. }


Which command-line invocation will produce the output found?


A
java -Dx=y x y z
B
java -Px=y x y z
C
java -Dx=y x x y z
D
java -Px=y x x y z
E
java x x y z -Dx=y
F
java x x y z -Px=y

I thought since we are comparing the property "x" to args[1] the correct answer is A, both would be y, however the exam says the answer is c. Please provide guidance.

[Ivan Ivanic]

in answer A, y is args[0] and z is args[1]
args is array, thus zero indexed...

[Christophe Verré]

Command line flags are not part of the main method arguments. You could see that by looping through the args parameter.

for(String arg:args) {
System.out.println(arg);
}

If you type "java" at the prompt, you'll some help, looking like that :
Usage: java [-options] class [args...]
(to execute a class)
or java [-options] -jar jarfile [args...]
(to execute a jar file)

This [-options] like -D are not part of the command line arguments. The [args...] are.

A
java [-Dx=y] x [y z] : property x = y. args[1] = z
B
java [-Px=y] x [y z] : -P ??
C
java [-Dx=y] x [x y z] : property x = y. args[1] = y
D
java [-Px=y] x x y z : -P ??
E
java x [x y z -Dx=y] : property x does not exist. args[1] = y
F
java x [x y z -Px=y] : property x does not exist. args[1] = y