Why I have to surround with try/cacth

Question

I have method

private void writeObject(ObjectOutputStream oos) throws IOException

In body I write keySet of some HashMap

        for(E e : map.keySet()) {
        oos.writeObject(e);
    }

And it's look OK But if I want to replase this code on

map.forEach((k, v) -> oos.writeObject(k));

I have to surround it with try/catch. Like this

        map.forEach((k, v) -> {
        try {
            oos.writeObject(k);
        } catch (IOException e) {
            e.printStackTrace();
        }
    });

And I can't understand for what

Update I can't understand why I need to processed exception in method body if I anounce in method title that I want it to throw away.

Are you saying that when you use ` for(E e : map.keySet()) { oos.writeObject(e); }` you dont have to use `try catch` but when replace code you have to use `try catch` ? — mahfuj asif, Aug 26 '20 at 10:11

score 1 · Answer 1 · answered Aug 26 '20 at 10:19

1

That is because forEach() takes Consumer as argument. And Consumer isn't declared throws any checked exception. So your lambda should also be Consumer and do not throw any checked exceptions. So any checked exception should be caught in you lambda body.

answered Aug 26 '20 at 10:19

Kirill

49
8

thank you. I will go to read more about lambda – boomzin Aug 26 '20 at 10:29

score 0 · Answer 2 · answered Aug 26 '20 at 10:14

The try block will execute a sensitive code which can throw exceptions The catch block will be used whenever an exception (of the type caught) is thrown in the try block

The throws keyword in the method prototype is used to specify that your method might throw exceptions of the specified type. It's useful when you have checked exception (exception that you have to handle) that you don't want to catch in your current method.

Why I have to surround with try/cacth

2 Answers2