I have a String:
String ints = "1, 2, 3";
I would like to convert it to a list of ints:
List<Integer> intList
I am able to convert it to a list of strings this way:
List<String> list = Stream.of("1, 2, 3").collect(Collectors.toList());
But not to list of ints.
Any ideas?
You need to split the string and make a Stream out of each parts. The method splitAsStream(input) does exactly that:
Pattern pattern = Pattern.compile(", ");
List<Integer> list = pattern.splitAsStream(ints)
.map(Integer::valueOf)
.collect(Collectors.toList());
It returns a Stream<String> of the part of the input string, that you can later map to an Integer and collect into a list.
Note that you may want to store the pattern in a constant, and reuse it each time it is needed.
", "), maybe this solution with splitAsStream will be faster than the other. This needs to be measured.
Pattern.splitAsStream() method. Excellent!
Pattern.compile(", ", Pattern.LITERAL); to hint to the engine that there is no real pattern matching. Of course, the engine will find out itself without the flag, but specifying the flag skips the process of analyzing the pattern.Regular expression splitting is what you're looking for
Stream.of(ints.split(", "))
.map(Integer::parseInt)
.collect(Collectors.toList());
Arrays.stream if the input is an array, i.e. when there is not a real varargs invocation. This makes it clear that we stream over an array and will work correctly for arrays of primitive types instead of creating a single element stream. For this specific case, both will do the same.Arrays.asList a varargs method has been considered a design mistake, as it contradicts the purpose of creating a wrapper around an existing array (e.g. the array can be modified through the returned List). Java 9 is going to fix that. There, you can use List.of(…) to create an immutable list of arbitrary size (true varargs semantics) and Arrays.asList(array) to wrap an array in a mutable List (still being varargs due to compatibility constraints).First, split the string into individual numbers, then convert those (still string) to actual integers, and finally collect them in a list. You can do all of this by chaining stream operations.
String ints = "1, 2, 3";
List<Integer> intList = Stream
.of(ints.split(", "))
.map(Integer::valueOf)
.collect(Collectors.toList());
System.out.println(intList); // [1, 2, 3]
You can just use the Array function asList, and then convert it the java8 way.
Don't forget to remove the white spaces.
List<Integer> erg = Arrays.asList(ints.replace(" ", "").split(",")).stream().map(Integer::parseInt).collect(Collectors.toList());
EDIT: Sorry i didn't see that it was a single string, thought it was a array of String.
"1, 2, 3". Did you mean:Stream.of("1", "2", "3")?