Throw an exception if an Optional<> is present

Question

Let's say I want to see if an object exists in a stream and if it is not present, throw an Exception. One way I could do that would be using the orElseThrow method:

List<String> values = new ArrayList<>(); values.add("one"); //values.add("two");  // exception thrown values.add("three"); String two = values.stream()         .filter(s -> s.equals("two"))         .findAny()         .orElseThrow(() -> new RuntimeException("not found")); 

What about in the reverse? If I want to throw an exception if any match is found:

String two = values.stream()         .filter(s -> s.equals("two"))         .findAny()         .ifPresentThrow(() -> new RuntimeException("not found")); 

I could just store the Optional, and do the isPresent check after:

Optional<String> two = values.stream()         .filter(s -> s.equals("two"))         .findAny(); if (two.isPresent()) {     throw new RuntimeException("not found"); } 

Is there any way to achieve this ifPresentThrow sort of behavior? Is trying to do throw in this way a bad practice?

Answer 1

You could use the ifPresent() call to throw an exception if your filter finds anything:

    values.stream()             .filter("two"::equals)             .findAny()             .ifPresent(s -> {                 throw new RuntimeException("found");             });