Menu
I understand that a lambda in java cannot throw a checked exception, but can throw a RuntimeException, but why does the below code require brackets?
Map<String, Integer> m = new HashMap<>();
Integer integer = m.computeIfAbsent("", s -> {throw new IllegalArgumentException("fail");});
Why can't you have?
m.computeIfAbsent("", s -> throw new IllegalArgumentException("fail"));
Is it due to the assumption of the compiler that it would return in this instance an int, so therefor can't have a return of an exception, even though its thrown?
444
If Lambda encounters an error, it returns an exception type, message, and HTTP status code that indicates the cause of the error. The client or service that invoked the Lambda function can handle the error programmatically, or pass it along to an end user.
The most straightforward way would be to use a try-catch block, wrap the checked exception into an unchecked exception and rethrow it: List<Integer> integers = Arrays. asList(3, 9, 7, 0, 10, 20); integers. forEach(i -> { try { writeToFile(i); } catch (IOException e) { throw new RuntimeException(e); } });
A lambda expression body can't throw any exceptions that haven't specified in a functional interface. If the lambda expression can throw an exception then the "throws" clause of a functional interface must declare the same exception or one of its subtype.
For Lambda expressions, the compiler doesn't translate them into something which is already understood by JVM. Lambda syntax that is written by the developer is desugared into JVM level instructions generated during compilation, which means the actual responsibility of constructing lambda is deferred to runtime.
The Java Language Specification describes the body of a lambda expression
A lambda body is either a single expression or a block (§14.2).
This, however,
throw new IllegalArgumentException("fail")
is the throw statement, not an expression. The compiler therefore rejects it as the lambda expression's body.
You can go down the rabbit hole and learn what all the types of expressions are, here (follow the grammar).
103
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
