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javafunctional-programmingjava-8
Irina Rapoport
Irina Rapoport

Reputation: 1692

How to convert a string to a boolean[] array using Java 8 streams?

The * character converts to true, everything else to false.

This answer shows how to convert to Boolean[], but I seek to convert to an array of scalar booleans.

java8 lambda: convert a String of 0's and 1's to basic array of booleans

Upvotes: 1

Views: 1547

Answers (2)

Holger
Holger

Reputation: 298233

Consider using a BitSet instead, which is the more efficient storage structure

BitSet bs = IntStream.range(0, string.length())
                     .filter(i -> string.charAt(i)=='*')
                     .collect(BitSet::new, BitSet::set, BitSet::or);

You can test the bits using bs.get(index), which is not worse than array[index].

Note that a BitSet also has a stream() method which produces an IntStream of the indices of true value, equivalent to the stream we used for constructing the BitSet. So if you can’t get away without an array at some point, you could create it like

boolean[] array = new boolean[string.length()];
bs.stream().forEach(i -> array[i]=true);

Upvotes: 2

khelwood
khelwood

Reputation: 59112

If the requirements are simply to convert to the described boolean array and to use streams, you can do it like this:

boolean[] result = new boolean[string.length()];
IntStream.range(0, string.length()).forEach(n -> result[n] = (string.charAt(n)=='*'));

Upvotes: 7

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