What is the point in java of including in the method header throws <exception>?

[Tom]

For instance,

public class Adder
{

public static void main(String[] args)
{
double result;

try
{
result = add(args);
System.out.println(args[0]+"+"+args[1]+": "+result);
}
catch (ArrayIndexOutOfBoundsException aioobe)
{
System.out.println("Too few operands.");
}
}




public static double add(String[] terms)
throws ArrayIndexOutOfBoundsException
{
double left, result, right;
String operator;

left = 0.0;
right = 0.0;


try
{
left = Double.parseDouble(terms[0]);
}
catch (NumberFormatException nfe)
{
left = 0.0;
}

try
{
right = Double.parseDouble(terms[1]);
}
catch (NumberFormatException nfe)
{
right = 0.0;
}


result = right + left;

return result;
}
}

Why isn't just having a try catch block good enough?