How can I throw CHECKED exceptions from inside Java 8 streams?

Question

How can I throw CHECKED exceptions from inside Java 8 streams/lambdas?

In other words, I want to make code like this compile:

public List

        

Answer 1

You can also write a wrapper method to wrap unchecked exceptions, and even enhance wrapper with additional parameter representing another functional interface (with the same return type R). In this case you can pass a function that would be executed and returned in case of exceptions. See example below:

private void run() {
    List list = Stream.of(1, 2, 3, 4).map(wrapper(i ->
            String.valueOf(++i / 0), i -> String.valueOf(++i))).collect(Collectors.toList());
    System.out.println(list.toString());
}

private  Function wrapper(ThrowingFunction function, 
Function onException) {
    return i -> {
        try {
            return function.apply(i);
        } catch (ArithmeticException e) {
            System.out.println("Exception: " + i);
            return onException.apply(i);
        } catch (Exception e) {
            System.out.println("Other: " + i);
            return onException.apply(i);
        }
    };
}

@FunctionalInterface
interface ThrowingFunction {
    R apply(T t) throws E;
}