How create array that only has 0 and 1 values?

Question

Hi, I have a problem with my homework assignment. I need to populate array with digits that only 0 or 1. Any other digits, alphabetical characters and symbols should not be in the array and method should throw exception (Only digits or Only 0 or 1 values), in this case array should not be created. Could someone help me figure out the problem. Here is the code:
public BinaryNumber(String str) {
data = new int [str.length()];
try{
for(int i = 0; i < str.length(); i++){
char ch = str.charAt(i);
if(!Character.isDigit(str.charAt(i))) {
throw new Exception("Not digit!");
}
if (ch == '0' || ch == '1') {
data[i] = Character.getNumericValue(ch);
}
else {
throw new Exception("Only 0 and 1 are allowed!");
}
}
}catch (Exception excpt) {
System.out.println(excpt.getMessage());
}
}
public static void main(String [] args) {
       BinaryNumber data1 = new BinaryNumber("ggiuyuihk");
       System.out.println(data1);
}
After running the program in main, I got message but also I've got array populated with same amount 0 values

Answer 1

if you wish set data to null, do it after catch

} catch (Exception excpt) {
data = null;
System.out.println(excpt.getMessage() );
}

but better is throw IllegalArgumentException without try.
And optionally catch it in the main() like api user programmer for friendly result on screen

api throws Exceptions fast

Answer 2

Thank you zemiak! I will try your approach