I have a String hashset (called "names") and I want to remove from it all the Strings that contains at least one char that isn't a capital letter. I wrote this code and it doesn't work:
Iterator<String> iterator=names.iterator();
while(iterator.hasNext()) {
for (int i=0; i<iterator.next().length(); i++) {
if (iterator.next().charAt(i) < 'A' || iterator.next().charAt(i) > 'Z') {
names.remove(iterator.next());
}
}
}
Another solution if you are using Java-8 by using removeIf and regex [A-Z]+ like so :
Set<String> names = //.. some inputs
names.removeIf(str -> !str.matches("[A-Z]+")); // remove if not matches [A-Z]+
Note in this solution you don't need to convert your list to an iterator at all, and not need to check your characters by a loop, just you can match by regex.
There are three issues with your code:
You should call iterator.next() once in each iteration of the while loop (since each call to iterator.next() returns a different element).
You should use the Iterator's remove method to delete the current element (that's the only valid way to make a structural change in a Collection while iterating over it).
You should break out of the loop when you remove the current element, in order to avoid trying to remove the same element multiple times.
Iterator<String> iterator = names.iterator();
while (iterator.hasNext()) {
String str = iterator.next();
for (int i = 0; i < str.length(); i++) {
if (str.charAt(i) < 'A' || str.charAt(i) > 'Z') {
iterator.remove();
break;
}
}
}
