EXPT NO. 1

Echoing Command-Line Arguments

NON-NUMERIC

1.   class CommandLineExample{  

2.   public static void main(String args[]){  

3.   System.out.println("Your first argument is: "+args[0]);  

4.   }  

5.   }  

1.  compile by > javac CommandLineExample.java  

2.  run by > java CommandLineExample sonoo  

Output: Your first argument is: sonoo

1.  Public class A{  

2.  public static void main(String args[]){  

3.    

4.  for(int i=0;i<args.length;i++)  

5.  System.out.println(args[i]);  

6.    

7.  }  

8.  }  

compile by > javac A.java  

run by > java A bvcoe NM 1 3 abc  

Output: bvcoe

       NM

       1

       3

       abc

The Echo example displays each of its command-line arguments on a line by itself:

public class Echo {

    public static void main (String[] args) {

        for (String s: args) {

            System.out.println(s);

        }

    }

}

The following example shows how a user might run Echo. User input is in italics.

java Echo Drink Hot Java

Drink

Hot

Java

Note that the application displays each word — Drink, Hot, and Java — on a line by itself. This is because the space character separates command-line arguments. To have Drink, Hot, and Java interpreted as a single argument, the user would join them by enclosing them within quotation marks.

java Echo "Drink Hot Java"

Drink Hot Java

Parsing Numeric Command-Line Arguments

If an application needs to support a numeric command-line argument, it must convert a String argument that represents a number, such as "34", to a numeric value. Here is a code snippet that converts a command-line argument to an int:

int firstArg;

if (args.length > 0) {

    try {

        firstArg = Integer.parseInt(args[0]);

    } catch (NumberFormatException e) {

        System.err.println("Argument" + args[0] + " must be an integer.");

        System.exit(1);

    }

}

parseInt throws a NumberFormatException if the format of args[0] isn't valid. All of the Number classes — Integer, Float, Double, and so on — have parseXXX methods that convert a String representing a number to an object of their type.