Code Problem! Please Help!

Question

Hello Everyone,
I have a problem with a code that I have been working on for days. I keep getting this error message:
exception in thread main java.lang.ArrayIndexOutOfBoundsException
I would really appreciate your help. I am a beginner java programmer, so I will try my best to understand your solutions.
Thank You,
Here is my code:
public class MonetaryTextH9P4
static String inputString;
static int dotAt;
public static void main( String[] args )
inputString = args[0];
dotAt = inputString.indexOf( '.' );
if( inputValidate() )
simplify();
System.out.println( toMonetaryText() );
else
System.out.println( "Invalid input" );
// check input has 2 decimal digits and only numbers
static boolean inputValidate()
char c;
if( inputString.length() != dotAt + 3 )
return false;
for( int i = 0; i < inputString.length(); i++ )
if( i != dotAt )
c = inputString.charAt(i);
if( !( c >= 48 && c <= 57 ) )
return false;
return true;
// removes zeros at beginning of number ( not in case 0.xx )
public static void simplify()
boolean ready = false;
while( !ready && dotAt < 1 )
if( inputString.charAt(0) == '0' )
inputString = inputString.substring(1);
dotAt--;
else
ready = true;
static String toMonetaryText()
// second digit of integer/decimal part
int tens = 0;
// divide input string into integer part and decimal part
String intpart = inputString.substring( 0, dotAt ),
decpart = inputString.substring( dotAt + 1 );
String output = "";
// if there is a third digit in the integer part
if( intpart.length() == 3 )
output += translate(Integer.parseInt(intpart.substring( 0, 1 ) ) ) + " hundred and ";
// if there is at least a second digit in the integer part
if( intpart.length() > 1 )
tens = Integer.parseInt( intpart.substring(intpart.length()-2, intpart.length()-1 ) );
// special case: ten to nineteen
if( tens == 1 )
output += translate( Integer.parseInt(intpart.substring(intpart.length()-2 ) ) );
// twenty- to ninety-something
if( tens > 1 )
output += translate( tens * 10 );
// first digit hasn't already been expressed ( teens or exact tens )
if( tens != 1 && Integer.parseInt( intpart.substring( intpart.length()-1 ) ) != 0 )
output += translate( Integer.parseInt(intpart.substring( intpart.length()-1 ) ) );
// if integer part not zero
if( !( Integer.parseInt( intpart.substring( intpart.length()-1 ) ) == 0
&& intpart.length() == 1 ) )
output += " dollars and ";
// roughly analogous with decimal part:
tens = Integer.parseInt( decpart.substring( 0, 1 ) );
if( tens == 1 )
output += translate( Integer.parseInt( decpart ) );
if( tens > 1 )
output += translate( tens * 10 );
if( tens != 1 && Integer.parseInt( decpart.substring(1) ) != 0 )
output += translate( Integer.parseInt( decpart.substring(1) ) );
if( decpart.equals( "00" ) )
output += "zero";
output += " cents.";
return output;
static String translate( int num )
switch( num )
case 0:
return "zero";
case 1:
return "one";
case 2:
return "two";
case 3:
return "three";
case 4:
return "four";
case 5:
return "five";
case 6:
return "six";
case 7:
return "seven";
case 8:
return "eight";
case 9:
return "nine";
case 10:
return "ten";
case 11:
return "eleven";
case 12:
return "twelve";
case 13:
return "thirteen";
case 14:
return "fourteen";
case 15:
return "fifteen";
case 16:
return "sixteen";
case 17:
return "seventeen";
case 18:
return "eighteen";
case 19:
return "nineteen";
case 20:
return "twenty";
case 30:
return "thirty";
case 40:
return "fourty";
case 50:
return "fifty";
case 60:
return "sixty";
case 70:
return "seventy";
case 80:
return "eighty";
case 90:
return "ninety";
default:
return "";

Answer 1

If you run the application without passing an argument, you will get ArrayIndexOutOfBoundsException at the line "inputString = args[0]" because you are accessing the first element in the String array "args", but the String array is empty!
public static void main( String[] args )
inputString = args[0];You should add the following defensive code to check the length of the array first.
    public static void main( String[] args ) {
        if (args.length == 0) {
            System.out.println("usage: java MonetaryTextH9P4 [arg]");
            return;
        inputString = args[0];