How to filter a List of strings and split them and return an Array in Java 8-CodePudding

I have to filter strings from a list containing lines shown below.

"15:09:00 SOME TEXT SOME TEXT 088"
"15:09 SOME TEXT 1546 AMOUNT"
"15:09:06 SOME TEXT 1546 AMOUNT"
"13:03:00 SOME TEXT TEXT TEXT 00"

I want to get elements that start with 15:09 and then split the line by white space. The split() method returns an array.

How to collect this to an array using streams?

I've tried the code below. I don't understand how to collect the data to array, that's why here method collect() returns a list.

String [] parts = myList.stream()
    .filter(p -> p.startsWith("19:01 "))
    .map(l -> l.split("\\s "))
    .collect(Collectors.toList());

CodePudding user response：

split returns an array

You need to apply flatMap() in order to produce a stream of Strings from a stream of Strings[].

And in order to collect the stream data into an array, you need to apply toArray(), which expects a function that produces an array of the desired type, as terminal operation:

public static void main(String[] args) {
    List<String> myList = 
        List.of("15:09:00 SOME TEXT SOME TEXT 088",
                "15:09 SOME TEXT 1546 AMOUNT",
                "15:09:06 SOME TEXT 1546 AMOUNT",
                "13:03:00 SOME TEXT TEXT TEXT 00");
    
    String[] parts = getParts(myList, "15:09:06", "\\s ");

    System.out.println(Arrays.toString(parts));
}

public static String[] getParts(List<String> source, String prefix, String delimiter) {
    return source.stream()
        .filter(str -> str.startsWith(prefix)) // Stream<String>
        .map(str -> str.split(delimiter))      // Stream<String[]>
        .flatMap(Stream::of)                   // Stream<String>
        .toArray(String[]::new);
}

Output

[15:09:06, SOME, TEXT, 1546, AMOUNT]

CodePudding user response：

if I were in you I'll do this for to select a single char of the string, if char is equals " " use the substring metod to copy the string in an arrylist and delite the string selected from the text