How would you convert A string into A Array/ArrayList

Question

I have this code in which I want to convert a String (e.g. [15, 52, 94, 20, 92, 109]) to an Array/ArrayList.

I have tried this code:

ArrayList<Byte> sdata = new ArrayList<>();
String bytessonvert = new String();
boolean run = true;
System.out.println("Enter Data: ");
String bytes = input.nextLine();
Bytes = bytes.substring(1, bytes.length());
for (int i = 0; i < bytes.length(); i++) {
    if (Objects.equals(bytes.substring(i, i), " ")) {
        sdata.add((byte) Integer.parseInt(bytessonvert));
        bytessonvert = "";
    } else if (bytes.substring(i, i) == ",") {
        sdata.add((byte) Integer.parseInt(bytessonvert));
        bytessonvert = "";
    } else {
        bytessonvert = bytessonvert + bytes.substring(i, i);
    }
}

"a, b, c".split(",", -1) will result in an array like new String[] { "a", " b", " c"} - using split("\\h*,\\h*", -1) it will even eliminate eventual spaces before and after the , || -1 to avoid removing trailing empty strings — user16320675
– user16320675, Commented Jul 8, 2022 at 6:16

Basil Bourque · Accepted Answer · 2022-07-08 18:40:01Z

1

No need for bytes. Java handles text well.

Use String#split to make an array of the parts.

Make a stream of that array of string parts.

Parse each String part into a Integer object using Stream#map to make another stream of the new objects.

Collect these new Integer objects into an unmodifiable List.

List < Integer > integers = 
    Arrays
    .stream( 
        "15, 52, 94, 20, 92, 109".split( ", " ) 
    )
    .map( Integer :: valueOf )
    .toList() ;

See this code run live at Ideone.com.

edited Jul 8, 2022 at 18:40

answered Jul 8, 2022 at 6:18

Basil Bourque

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1 Comment

user16320675 Over a year ago

alternative: Pattern.compile(", ").splitAsStream("15, 20, 30").map(Integer::valueOf).toList() (not sure if it is easier to read [since it starts with a regular expression], probably only a matter of preference)

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