help with java

[stettybet0]

sorry for lack of a descriptive title, but I don't know how to describe my problem!

I'm looking to do this:

I have a program called "program" It is run via the command "java" in the command line. I have 3 strings in it: string "a", string "b", and string "c". Here's what I need to have happen:

When the user enters "java program duck cow moose". I want "duck" to be stored in string "a", "cow" to be stored in string "b", and "moose" to be stored in string "c". Also, If the person only enters "java program duck cow", then I want "duck" to be stored in string "a", "cow" to be stored in string "b", and for string "c" to remain empty.

I have no idea how to go about this... I know how to make it so user input goes into a string, but only after the program is running. How do I do it in the way I described?

Thanks,
stettybet0

[System_Error]

public static void main(String[] args)
{
}

args will contain the passed arguments. args[0] = first argument, args[1] = second argument, etc.

[stettybet0]

just to make sure I understand:

so, if i put

string a = args[0]
string b = args[1]
string c = args[2]

that would give me what I want?

[System_Error]

just to make sure I understand:

so, if i put

string a = args[0]
string b = args[1]
string c = args[2]

that would give me what I want?

Sort of. Your code would require exactly 3 arguments, and since you might not have three you need to do some range checking.

ie: if (args.length > 0)

[stettybet0]

to check whether args[0] exists, would i do "if (args[0].length > 0)" ?

[System_Error]

if (args.length > 0) ensures that there's at least one argument, so args[0] would exist in this case. It might be helpful to know that args.length returns the number of arguments. If you know there won't be more than 3 arguments, then you can do something like this:

   public static void main(String[] args)
   {
        String a="", b="", c="";
	if (args.length > 0) a = args[0];
	if (args.length > 1) b = args[1];
	if (args.length > 2) c = args[2];
   }

or

   public static void main(String[] args)
   {
        String a="", b="", c="";
	switch(args.length)
	{
		case 1:
			a = args[0];
			break;
		case 2: 
			a = args[0];
			b = args[1];
			break;
		case 3:
			a = args[0];
			b = args[1];
			c = args[2];
			break;
	}
   }

This could be done in many different ways.

[stettybet0]

here's what I tried... with no success:

class program {
 
   public static void main (String[] args) {
 
      String a = null;
      String b = null;
      String c = null;
 
      if (args[0].length > 0) {
         String a = args[0];
      }
      if (args[1].length > 0) {
         String b = args[1];
      }
      if (args[2].length > 0) {
         String c = args[2];
      }
      System.out.println(a);
      System.out.println(b);
      System.out.println(c);
   }
}

edit:
saw ur new post... trying that out now.

[System_Error]

Wow! We just posted at the exact same time! You are very close, but check my listings about you.

I would go for this:

   public static void main(String[] args)
   {
        String a="", b="", c="";
	if (args.length > 0) a = args[0];
	if (args.length > 1) b = args[1];
	if (args.length > 2) c = args[2];
   }

[System_Error]

Of course, if you just want to print out the args, then all you have to do is this:

   public static void main(String[] args)
   {
	for (int i=0; i<args.length; ++i) 
		System.out.println(args[i]);
   }

[stettybet0]

Here's what I ended up with: (it works great)

class program {
 
   public static void main (String[] args) {
 
      String a = "";
      String b = "";
      String c = "";
 
      if (args.length > 0 && args.length < 2) {
         a = args[0];
         System.out.println(a);
      }
      if (args.length > 1 && args.length < 3) {
         a = args[0];
         b = args[1];
         System.out.println(a);
         System.out.println(b);
      }
      if (args.length > 2 && args.length < 4) {
         a = args[0];
         b = args[1];
         c = args[2];
         System.out.println(a);
         System.out.println(b);
         System.out.println(c);
      }
      if (args.length > 3 || args.length < 1) {
         System.out.println("Enter only 1, 2, or 3 arguments!");
      }
   }
}

anything you see that i did wrong (or inefficiently)?

thanks for the help.

[stettybet0]

I have also come up with this way:

class program {
 
   public static void main (String[] args) {
 
      String a = "";
      String b = "";
      String c = "";
 
      if (args.length > 3 || args.length < 1) {
         System.out.println("Enter only 1, 2, or 3 arguments!");
         System.exit(0);
      }
      if (args.length > 0) {
         a = args[0];
         System.out.println(a);
      }
      if (args.length > 1) {
         b = args[1];
         System.out.println(b);
      }
      if (args.length > 2) {
         c = args[2];
         System.out.println(c);
      }
   }
}

Which way do you think is more "orthodox"? (ie. it would please my old-skool teacher)

[stettybet0]

A third way: (only difference is that I don't define the variables before I need them... just learned that you usually shouldn't )

class program {
 
   public static void main (String[] args) {
 
      if (args.length > 3 || args.length < 1) {
         System.out.println("Enter only 1, 2, or 3 arguments!");
         System.exit(0);
      }
      if (args.length > 0) {
         String a = args[0];
         System.out.println(a);
      }
      if (args.length > 1) {
         String b = args[1];
         System.out.println(b);
      }
      if (args.length > 2) {
         String c = args[2];
         System.out.println(c);
      }
   }
}

This way seems the best to me. My teacher always says that if you can do the same thing with less code, then do it!

[System_Error]

If you are just printing the variables out, then there's no point in even creating them:

public static void main(String[] args)
{
   if (args.length > 0 && args.length < 4)
   {
       for (int i=0; i<args.length; ++i)
         System.out.println(args[i]);
   }
   else
   {
       System.out.println("You must supply at least one argument and less than four");
   }
}

No variables needed, but of course, if this is an assignment and it's required then go with your last try.

[stettybet0]

Yeah, I needed variables. Thanks for your help!