Programming

public class prob4
 {
    public static void main(String args[])
    {
      String ArgumentFromCommandLine = args[0];
	  int time = Integer.parseInt(ArgumentFromCommandLine);    

        switch ( time )
    {
        case 0:
            ???;
            break;
        case 1:
            ???;
            break;
        case 2:
            ???;
            break;
        case 3:
            ???;
            break;
        default:
            System.out.println("Invalid");
    }
	
    }

}

import java.util.Date; // mandatory only for the "current date and time" part

public class prob4
 {
    public static void main(String args[])
    {

    String ArgumentFromCommandLine = "";
    int time = 0;

    // exit program if the supplied argument is not an integer OR
    // if no or too many arguments were supplied
    if (args.length == 1) {
        try {
        ArgumentFromCommandLine = args[0];
            time = Integer.parseInt(ArgumentFromCommandLine);
        } catch (NumberFormatException e) {
            System.err.println("Argument " + args[0] + " must be an integer.");
            System.exit(1);
        }
    }
    else {
        System.err.println("No or too many arguments were supplied.");
            System.exit(1);
    }

    // collect all values
    Long utms = System.currentTimeMillis(); // UNIX time in milliseconds
    Long uts = utms / 1000; // UNIX time in seconds
    Long utd = uts / 86400; // UNIX time in days
    Date dateandtime = new Date(); // Current date and time, default format

    // print requested value
        switch ( time )
    {
        case 0:
            System.out.println("Milliseconds since 1970: " + utms);
            break;
        case 1:
            System.out.println("Seconds since 1970: " + uts);
            break;
        case 2:
            System.out.println("Days since 1970: " + utd);
            break;
        case 3:
            System.out.println("Current date and time: " + dateandtime);
            break;
        default:
            System.out.println("Invalid");
    }

    }

}

$
$ cat -n ParseInteger.java
     1  public class ParseInteger {
     2      public static void main (String[] args) {
     3          if (args.length == 1) {
     4              String strParam = args[0];
     5              System.out.println("Input string parameter                  = [" + strParam + "]");
     6              System.out.print  ("Integer value of input string parameter = ");
     7              System.out.println(Integer.parseInt(strParam));
     8          }
     9      }
    10  }
$
$ javac ParseInteger.java
$
$ java ParseInteger "-000456"
Input string parameter                  = [-000456]
Integer value of input string parameter = -456
$
$ java ParseInteger "-00"
Input string parameter                  = [-00]
Integer value of input string parameter = 0
$
$ java ParseInteger "+00"
Input string parameter                  = [+00]
Integer value of input string parameter = 0
$
$ java ParseInteger "000"
Input string parameter                  = [000]
Integer value of input string parameter = 0
$
$ java ParseInteger "1234"
Input string parameter                  = [1234]
Integer value of input string parameter = 1234
$
$ java ParseInteger "+123"
Input string parameter                  = [+123]
Integer value of input string parameter = 123
$
$ java ParseInteger ""
Input string parameter                  = []
Integer value of input string parameter = Exception in thread "main" java.lang.NumberFormatException: For input string: ""
        at java.lang.NumberFormatException.forInputString(Unknown Source)
        at java.lang.Integer.parseInt(Unknown Source)
        at java.lang.Integer.parseInt(Unknown Source)
        at ParseInteger.main(ParseInteger.java:7)
$
$