Printing "Hi Hello Bye!!"

[Gangadhar Shetty]

In one of the interview I have to face the below question.

There is only one print statement in main function. i.e. System.out.println("Hello"); without altering/ adding new statements to the main function get me an output of "Hi Hello Bye!".

I wrote the below code snippet

public class Test1{
static{
System.out.println("Hi");
}

public static void main(String [] args){
System.out.println("Hello"); //no extra statements here
}
}

The above code successfully producing the output "Hi Hello" since I knew that once we enter to a class irrespective of creating object for that class, static block will get executed. But how to print "Bye!!" at last? Please some one help me to solve this problem.

Thanks in advance.

[Henry Wong]

One option you can try is using a shutdown hook -- code to be executed upon JVM shutdown. Take a look at the Runtime class for more info.

Henry

[Henry Wong]

BTW, not really a topic about jobs -- moving to the java in general forum.

Henry

[Raza Mohd]

you can extend the class and call main method .

That will solve you problem

Regards
Raza

[Joe San]

You could pass command line arguments...

[Gangadhar Shetty]

Raza Mohd wrote:you can extend the class and call main method .

That will solve you problem

Regards
Raza

Can you please elaborate it? Because even if I extend the class where can I put the print statement to print "Bye!" and where can I create object for the derived class? since the main requirement is 'nothing should be added to Main block'

[Gangadhar Shetty]

Jothi Shankar Kumar wrote:You could pass command line arguments...

I have already tried this option but couldn't prove it. Once you send command line arguments, it will be stored in 'args' array. Since this is local for the 'main' function, then how will you call this array out of 'main' block which will be out of scope.

Can you please elaborate your idea and correct me if my comments are wrong.

[Ernest Friedman-Hill]

Raza Mohd's answer would require that you invoke a different class from the command line, not this one, which I think is against the spirit of the question. Jothi Shankar Kumar's answer isn't an option. But Henry's answer is a good one, and likely the one the interviewer had in mind.

[Joe San]

System.out.println(args[0]);

Run it like java YourClass "Hi Hallo Bye"

[Joe San]

Ernest Friedman-Hill wrote:Raza Mohd's answer would require that you invoke a different class from the command line, not this one, which I think is against the spirit of the question. Jothi Shankar Kumar's answer isn't an option. But Henry's answer is a good one, and likely the one the interviewer had in mind.

Why isn't it an option?

[Ernest Friedman-Hill]

You'll have to show us some code to explain your idea.

[Sandeep Awasthi]

Henry Wong wrote:
One option you can try is using a shutdown hook -- code to be executed upon JVM shutdown. Take a look at the Runtime class for more info.

Henry

This is what Henry mean

[ EFH: Code deleted -- JavaRanch is NotACodeMill ]

[Rohan kanade]

Henry Wong wrote:
One option you can try is using a shutdown hook -- code to be executed upon JVM shutdown. Take a look at the Runtime class for more info.

Henry

Or you can do this.

 public class test {

static {
System.out.println("hi");
}



public static void main(String []args)
{
System.out.println("Hello");
}

static {
main(null);
System.out.println("bye");
System.exit(0);
}
}   

or you can add a finalize() method and say "bye" in that. but then you will have to create a object and point it to null then call the Garbage collector, plus there is no guarantee that GC will be called in time.

If you feel like impressing the interviewers , then try using the Runtime.exec() methods to call the host operating system's echo command , just for fun.

[Rohan kanade]

Jothi Shankar Kumar wrote:

Ernest Friedman-Hill wrote:Raza Mohd's answer would require that you invoke a different class from the command line, not this one, which I think is against the spirit of the question. Jothi Shankar Kumar's answer isn't an option. But Henry's answer is a good one, and likely the one the interviewer had in mind.

Why isn't it an option?

because the constraint is that you cannot add anything to the main method, and how is one supposed to get the arguments passed to the main method without adding anything to the main method?

[Gangadhar Shetty]

Rohan kanade wrote:

Henry Wong wrote:
One option you can try is using a shutdown hook -- code to be executed upon JVM shutdown. Take a look at the Runtime class for more info.

Henry

Or you can do this.

 public class test {

static {
System.out.println("hi");
}



public static void main(String []args)
{
System.out.println("Hello");
}

static {
main(null);
System.out.println("bye");
System.exit(0);
}
}   

or you can add a finalize() method and say "bye" in that. but then you will have to create a object and point it to null then call the Garbage collector, plus there is no guarantee that GC will be called in time.

If you feel like impressing the interviewers , then try using the Runtime.exec() methods to call the host operating system's echo command , just for fun.

Thanks Rohan the code snippet is working fine.