Checking String for non-numbers

Here is one easy way to do it:

try {

int val = Integer.parseInt(str);

System.out.println("value is: " + val);

} catch (NumberFormatException exc) {

System.err.println("not a number");

}

It is probably not the fastest way, though...

Geoff

glevnera at 2007-7-9 23:21:03 >

Hi Aldrich!

A String is internally stored as a char[]. So you have the choice to either get each charecter with

charAt(int index)

or have everything copied to a new char array via

toCharArray()

and traverse that instead. It might turn out, that copying and traversing the array is faster than something like the following.

for (int i=0; i<test.length(); i++)

check(test.charAt(i));

(Because copying and traversing an array can be done in linear time, while the above for-loop needs n*(n+1)/2 steps for accessing all array-elements.) But haven't checked what's faster.

The check itself could look like this:

String test = "0123456789";

boolean check = true;

for (char c : test.toCharArray()) {

if (c>'9' || c<'0') {

check = false;

break;

}

}

ruehmkorfa at 2007-7-9 23:21:04 >