CODEWITHSUNDEEP
javajava-stream
OrangePot
OrangePot

Reputation: 1082

String to ArrayList<Long>

Currently i have:

String a = "123.5950,555,5973.1,6321.905,6411.810000000001,6591.855"

I can turn it into an array list of Strings then into array list of Longs: 

ArrayList<String> vals = new ArrayList<String>(Arrays.asList(a.split(","));
ArrayList<Long> longs = new ArrayList<>();

for(String ks : vals){
       longs.add(Long.parseLong(ks));
}

I tried to do this with Stream to make this more 'fun' but cant seem to be successful with this:

ArrayList<Long> longs = a.stream().map(Long::parseLong).collect(Collectors.toList());

I dont think the for loop is very elegant, how can i do it with Stream?

Edit: copied to original string wrong

Upvotes: 4

Views: 3991

Answers (3)

Joao Delgado
Joao Delgado

Reputation: 856

You need to create a stream from the result of String.split:

final List<Long> longs = Arrays
            .stream(a.split(","))
            .map(Long::parseLong)
            .collect(Collectors.toList());

Also, Collectors.toList() will return the List interface, not the concrete implementation ArrayList.

If you really need an array list, you'll need to copy it:

new ArrayList<>(longs);

Edit:
As @shmosel pointed out, you can collect directly to an array list with Collectors.toCollection(ArrayList::new)

Upvotes: 10

ck1
ck1

Reputation: 5443

String a = "123.5950.555,5973.1,6321.905,6411.810000000001,6591.855";
List<Double> doubleList = Arrays.stream(a.split(","))
        .map(Doubles::tryParse)
        .collect(Collectors.toList());
System.out.println(doubleList);

Note: this uses Doubles#tryParse from Guava.

Upvotes: 1

shmosel
shmosel

Reputation: 50716

You can't stream a String without splitting it up. Two ways to split to stream:

Arrays.stream(a.split(","))

or

Pattern.compile(",").splitAsStream(a)

Aside from that, collect(Collectors.toList()) returns List, not ArrayList. And I'm not sure why you expect parseLong() to work on those strings.

Upvotes: 4

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