Java: Catching lambda exceptions [duplicate]

Question

Not able to wrap stream object in a try/catch block.

I tried like this:

reponseNodes.stream().parallel().collect(Collectors.toMap(responseNode -> responseNode.getLabel(), responseNode -> processImage(responseNode)));

Eclipse started complaining underlining processImage(responseNode) and suggested that it needs to Surround with try/catch.

Then I updated to:

return reponseNodes.stream().parallel().collect(Collectors.toMap(responseNode -> responseNode.getLabel(), responseNode -> try { processImage(responseNode) } catch (Exception e) { throw new UncheckedException(e); }));

Updated code also did not work.

Could you type out the exact warning/error Eclipse is giving you? — Ken Slade
– Ken Slade, Commented Dec 6, 2015 at 6:13
Eclipse warning Surround with try/catch underlining processImage(responseNode). — Himanshu Yadav
– Himanshu Yadav, Commented Dec 6, 2015 at 6:18

Akash Thakare · Accepted Answer · 2015-12-06 06:21:51Z

2

There is no direct way to handle checked exceptions in lambadas, only option I came up with is just move the logic to another method which can handle it with try-catch.

For example,

List<FileReader> fr = Arrays.asList("a.txt", "b.txt", "c.txt").stream()
            .map(a -> createFileReader(a)).collect(Collectors.toList());
//....
private static FileReader createFileReader(String file) {
    FileReader fr = null;
    try {
        fr = new FileReader(file);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    return fr;
}

edited Dec 6, 2015 at 6:21

answered Dec 6, 2015 at 6:20

Akash Thakare

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2 Comments

Ken Slade Over a year ago

It's probably for the best. This is more readable.

Kevin Van Dyck Over a year ago

>lambadas best typo ever

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