Switch-Case

[P Jain]

Hi!
How do we take input from command prompt in Switch-Case.
I want to check some value and if it is equal to some specific value it should take input from command propmt.

[Jessica Sant]

keep in mind that a switch statement can only deal with integer values, so you'll need to convert all the values from the command line that you're evaluating to ints:

int value;
try {
   value = Integer.parseInt( <command line value here> );
   switch(value){
      case 1:
         // do stuff
         break;
      case 2:
         // do stuff
         break;
   }
}
catch( NumberFormatException e ){
   // what if the commandline value isn't a number??
}

[Layne Lund]

From the way I read the question, the subject line doesn't match. If you are asking about how to actually get the input from the command line, here's a simple example:

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

After compiling this program, an example run might look something like this:

$java PrintCommandLineArgs foo bar baz
arg #1=foo
arg #2=bar
arg #3=baz

I hope this helps illustrate how to access command line arguments. If you have any more questions, please feel free to ask.

Keep Coding!(TM)

Layne

Disclaimer: Use the code and output in this post at your own risk. I didn't take the time to compile it, so no warranty is given, explicit or implied, by its use.

[sever oon]

This program, called ParseCmdLine, provides you with a basis from which you can build your own UNIX-style command line parser.

class ParseCmdLine
{
    public static void main(String[] args) {
        int i = 0, j;
        String arg;
        char flag;
        boolean vflag = false;
        String outputfile = "";
 
        while (i < args.length && args[i].startsWith("-")) {
            arg = args[i++];
 
    // use this type of check for "wordy" arguments
            if (arg.equals("-verbose")) {
                System.out.println("verbose mode on");
                vflag = true;
            }
 
    // use this type of check for arguments that require arguments
            else if (arg.equals("-output")) {
                if (i < args.length)
                    outputfile = args[i++];
                else
                    System.err.println("-output requires a filename");
                if (vflag)
                    System.out.println("output file = " + outputfile);
            }
 
    // use this type of check for a series of flag arguments
            else {
                for (j = 1; j < arg.length(); j++) {
                    flag = arg.charAt(j);
                    switch (flag) {
                    case 'x':
                        if (vflag) System.out.println("Option x");
                        break;
                    case 'n':
                        if (vflag) System.out.println("Option n");
                        break;
                    default:
                        System.err.println("ParseCmdLine: illegal option " + flag);
                        break;
                    }
                }
            }
        }
        if (i == args.length)
            System.err.println("Usage: ParseCmdLine [-verbose] [-xn] [-output afile] filename");
        else
            System.out.println("Success!");
    }
}

It accepts one command line argument of each type: a word argument, an argument that requires an argument, and two flags. In addition, this program requires a filename. Here's the usage statement for this program:
usage: ParseCmdLine (-verbose) (-xn) (-output afile) filename

The arguments within parens are optional; the filename argument is required.

[P Jain]

Hi!
Thanks for all the replys.
I think the statement of the question submitted by me was not clear.
I want to know how can we take user input in Case statment like....


switch(choice)
{
case 1:
System.out.println("Enter your value :");
DataInputStream dis = new DataInputStream(System.in);
String str = dis.readLine();
System.out.println(str);
break;

case 2:
//some working

[P Jain]

Hi!
Thanks for all the replys.
I think the statement of the question submitted by me was not clear.
I want to know how can we take user input in Case statement like....


switch(choice)
{
case 1:
System.out.println("Enter your value :");
DataInputStream dis = new DataInputStream(System.in);
String str = dis.readLine();
System.out.println(str);
break;

case 2:
//some working
break;
}
whenever I use this type of code control will skip the case statement if choice is 1,it will not stay for taking user input.

how do I forced it to take user input in case 1.