Inaccurate for loop in Java array

Question

I've tried many hours to solve array task, but it seems to me that I'm stuck. The task is to create a program that prints the number of given command line parameters and lists them.

You gave 2 command line parameters.
Below are the given parameters:
1. parameter: 3455
2. parameter: John_Smith

My program starts from wrong index + I'm not sure about the given task. How does the program know how many parameters to use if that hasn't been initialized? Or am I just completely lost with the exercise?

This is what I've done:

    import java.util.Scanner;

public class ex_01 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        Scanner reader = new Scanner(System.in);

        int param = reader.nextInt();

        String[] matrix = new String[param];

        for (int i = 0; i < matrix.length; i++) {

            matrix[i] = reader.nextLine();// This is the part where my loop fails

        }

        System.out.println("You gave " + matrix.length
                + " command line parameters.\nBelow are the given parameters:");
        for (int i = 0; i < matrix.length; i++) {

            System.out.println(i + 1 + " parameter: " + matrix[i]);
        }

    }

}

And my own output:

3   //This is the number of how many parameters the user wants to input
2   // Where is the third one?
omg // 
You gave 3 command line parameters.
Below are the given parameters:
1 parameter: 
2 parameter: 2
3 parameter: omg

EDIT:

I DID IT! I DID IT!! After more Googling I found this:

        if (args.length == 0) {
        System.out.println("no arguments were given.");
    } else {
        for (String a : args) {

        }
    }

Then I just modified the program and Voilà the program compiled. Here is the whole program:

import java.util.Scanner;

public class Echo {


    public static void main(String[] args) {
        if (args.length == 0) {
            System.out.println("no arguments were given.");
        } else {
            for (String a : args) {

            }
        }

        System.out.println("You gave " + args.length
                + " command line parameters.\nBelow are the given parameters:");
        for (int i = 0; i < args.length; i++) {

            System.out.println(i + 1 + ". parameter: " + args[i]);
       }

        }

    }

I want to thank everyone who answered to this, the help was really needed! :)

Are you supposed to use the built-in args array?

tbodt
– tbodt

2013-07-25 11:30:37 +00:00
Commented Jul 25, 2013 at 11:30 — tbodt
– tbodt, Commented Jul 25, 2013 at 11:30
Definitely! :D And hey thanks!

Developous
– Developous

2013-07-25 13:15:05 +00:00
Commented Jul 25, 2013 at 13:15 — Developous
– Developous, Commented Jul 25, 2013 at 13:15

tbodt · Accepted Answer · 2013-07-25 11:35:33Z

2

Command line arguments are not text read by the program with Scanner and the like, they are strings specified in the args array that is an argument to main. It seems like you need to output the contents of that array instead of reading input and outputting it.

answered Jul 25, 2013 at 11:35

tbodt

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13 Comments

Kayaman Over a year ago

Why are you doing other people's homework for them? It's not a good way to learn if someone just gives you the answers.

tbodt Over a year ago

Yes, but he seems to be stuck on what "command line parameters" are. I'll delete my code and leave the guidance.

Developous Over a year ago

By the way do you guys know what is the best way to learn Java? I've tried various MOOCs, read over 20 java books, but seems that those haven't really helped me to understand fundamentals of Java.

Kayaman Over a year ago

@Javan00b Programming, and reading code. There's no shortcuts, and 20 books sounds excessive. There's only so much you can learn from books.

tbodt Over a year ago

I would say this is a separate question, but it would probably get put on hold as "primarily opinion-based". I learned java from an excellent tutorial, then by going to the local library's book sorting warehouse and getting several Java books there.

|

Nick Holt · Accepted Answer · 2013-07-25 11:36:59Z

2

I think you've confused what command line parameter means. A command line parameter is a parameter passed to the main method when the program runs, while System.in is capturing user input at the command line as the program runs.

The command line parameters are passed to the main method in the args parameter, so for example:

java MyClass one two three

Would pass the array ["one", "two", "three"] as the args parameter to the main method.

All you have to do then is use the args array to print the data information you require.

answered Jul 25, 2013 at 11:36

Nick Holt

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1 Comment

Developous Over a year ago

If I could I would also accept this as an answer, thank you! :)

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