I am trying to add an Object (Exception) to a Set, however it adds every Exception, eventhough some are duplicates.
debug
In my case duplicates are Exceptions which have the same Detail message.
How do I properly add the Exceptions to the HashSet only if the Exception.getDetails() doesn't already exist?
Is there another approach than a HashSet?
Performance is a criteria here, quadratic solutions (O(n^2))are not an option.
You have a few options:
hashcode and equals in your exception classTreeSet with a custom ComparatorMap<String, Exception> where the key is the getDetails() result (for example, a HashMap)You need to override how the Execptions are compared so it recognises duplicates the way you want. You can't do this for a HashSet but you can for TreeSet e.g.
Set<Exception> exceptions = new TreeSet<>(Comparator.comparing(Object::toString));
This example compares the toString which is the exception type and message in most cases.
If you really want to use a HashSet you need to wrap the Exception in a class which implements hashCode and equals the way you want.
If all you care about is the type and message you can store just the toString of each exception
final Set<String> exceptions = new HashSet<>();
public void addException(Exception e) {
exceptions.add(e.toString());
}
Map<String, Exception> which is O(1) per add.You need to redefine equals and hashCode methods.
If the detail is a String you can redefine them as follow
public boolean equals(Object obj) {
if (!(obj instanceof YourException)) {
return false;
}
return getDetail().equals(((YourException) obj).getDetail());
}
public int hashCode() {
return getDetail().hashCode();
}
Consider this code as a base to program. You have to check for null values for example.
Once redefined equals and hashCode inserting YourException in a TreeSet is an operation done in O(log(n)) where n is the size of the set, from javadoc:
This implementation provides guaranteed log(n) time cost for the basic operations (add, remove and contains).
messageFactory