Question

I am making this little program using command line arguments, I have like 90% of the work done. But I am trying to allow the user to enter non numerical values aswell..

User input/output example

Input:

$ java d1 4eb:16 10110110:2 407:8 2048:10

Output:

4eb base 16 is 1259 base 10
10110110 base 2 is 182 base 10
407 base 8 is 263 base 10
2048 base 10 is 2048 base 10

My only problem is with the first input because it has letters and it gives me a number exception error. Any help would be great, and I would prefer a help in the right direction, rather than just the answer. Thank you!

public class homework{
    public static void main (String[] args){
        int answer1=0,check1=0,check2=0,x=0, val=0,rad=0;   //holds integer values user gives and check for : handler, answer etc
        do{   //will continue to loop if no : inputted
        for (x=0;x<args.length;x++){

                check1=args[x].indexOf(":");        //checks input1 for the :
                if(check1==-1){System.out.println("No Colon Found in "+args[x]+".");check1=0;}
                else{
                    String numbers [] = args[x].split(":");     //splits the string at :
                    val = Integer.parseInt(numbers[0]);   //parses [0] to int and assigns to val
                    rad = Integer.parseInt(numbers[1]);     //parses [1] to int and assigns to rad
                    if(val==0||rad==0){System.out.println("The argument "+args[x]+" could not be converted.");check2=0;}
                    else{
                    for (int i = 0; val > Math.pow(rad, i); i++){
                        int digit = (val / (int) Math.pow(10, i)) % 10;
                        int digitValue = (int) (digit * Math.pow(rad, i));
                        answer1 += digitValue;}
                        answer1 = Integer.parseInt(numbers[0], rad);   //finds the answer in base10.
                        System.out.println(val+" base "+rad+" is "+answer1+" base 10.");  //gives user the results
            }}}}while(check1==-1);  }}  //if user forgot : loop

Answer 1

You need to specify the base when you first call parseInt. For example, if you are parsing a hexidecimal number, you need to specify:

val = Integer.parseInt(numbers[0], 16)

You receive this exception because you try to parse a hexadecimal number in base 10.

Maybe you should make the base another command line parameter. I will assume it is the first command line parameter. Then you could run:

int base = Integer.parseInt(args[0])
val = Integer.parseInt(number[0], base)