Question

Given the code below, is it possible to remove the index of p from the properties list using this style of for loop in Java?

List<Properties> propertiesList = new ArrayList<Properties>();
String keyToDelete = "blah";

for(Properties p : propertiesList) {
    if(p.getKey().equals(keyToDelete)) {
        propertiesList.remove(index) //How to remove the element at index 'p'
    }
}

This is how i would accomplish this with the other for loop

List<Properties> propertiesList = new ArrayList<Properties>();
String keyToDelete = "blah";

for(int i = 0; i < propertiesList.size(); i++) {
        if(p.getKey().equals(keyToDelete)) {
                propertiesList.remove(i);
        }
}

Answer 1

The way to do this is with an explicit Iterator (no school like the old school!).

Iterator<Properties> it = propertiesList.iterator();
while (it.hasNext()) {
    if (it.next().getKey().equals(keyToDelete)) {
        it.remove();
    }
}

Unlike the remove method on a list, the remove method on the iterator doesn’t cause a concurrent modification. It’s the only safe way to remove an element from a collection you’re iterating over. As the javadoc for that method says:

The behavior of an iterator is unspecified if the underlying collection is modified while the iteration is in progress in any way other than by calling this method.