String not able to match with asterisk (*) in java

Question

I am trying to give command line argument to this program. But it gives Invalid operator when operator is * eg 2 3 *

import java.io.*;

import java.util.*;

public class Operation{

    public static void main(String args[]){
        int num1, num2, res=0;
        try{
            Exception ex = new Exception();
            if(args.length < 3)
                throw(ex);
        }catch (Exception e){
            System.out.println("Illegal no. of arguments");
            System.exit(0);
        }
        try{
            Exception ex1 = new Exception();
            num1 = Integer.parseInt(args[0]);
            num2 = Integer.parseInt(args[1]);
            if(args[2].equals("+")) 
                res = num1 + num2;
            else if(args[2].equals("-")) 
                res = num1 - num2;  
            else if(args[2].equals("*")) 
                res = num1 * num2;
            else if(args[2].equals("/")) 
                res = num1 / num2;
            else
                throw(ex1);
        }catch (Exception e){
            System.out.println("Invalid Operator");
            System.exit(0);
        } 
        try{
            Exception ex2 = new Exception();
            if(res < 0)
                throw(ex2);
            else
                System.out.println("Result = " + res);
        }catch (Exception e){
            System.out.println("Result is negative");
        }       
    }
} 

Answer 1

Most likely, the * character will never arrive in your Java program. Typically, the shell that you use to invoke the java program will recognize it as wildcard and replace it with something; for example all files in the current directory. Have you tried "*" when invoking your program on the command line?

Alternatively, you could change your program: do not read the arguments from the command line; ask the user to type the values one by one, see Getting Keyboard Input