Exception handling – the old way

Let's write some code so that we can talk about exception handling. Take a look at the following:

def toInt(str: String): Int = str.toInt 

In the preceding code, the toInt is a function that takes a String value, which supposedly can be converted to a corresponding Int value. The definition looks okay, but as functional programmers, we are so used to trying out the function to see whether it does what it says (in the definition). Let's try out some calls to this function:

println(toInt("121")) 
println(toInt("-199")) 

The preceding code gives the following result:

121 
-199 

Things worked fine for us. We passed a number in a string format and got the corresponding integer values. But what if you try something like the following:

println(toInt("+ -199")) 

Say that we get something unexpected, some exception saying this:

Exception in thread "main" java.lang.NumberFormatException: For input string: "+ -199" 
   at java.lang.NumberFormatException.forInputString(NumberFormatException...