Using list stream: Arbitrary Object List Splice String

Directory arbitrary object List splicing string String. join method next introduces a more convenient processing method Stream stream merging string, splicing string

Arbitrary Object List Splice String

In the development, the data in List is often processed. One common processing method is splicing. Each element in List is spliced into an String through a specific separator. Before that, we often used the following method:

String. join method

As shown below:

public static void main(String[] args) {
        List<String> stringList = new ArrayList<>();
        stringList.add("a");
        stringList.add("d");
        stringList.add("k");
        System.out.println(String.join(",", stringList));
    }

Although this method is very easy to use, it has one defect, that is, the objects in List can only be characters or strings, so if it is other types of data or uncertain types of data, it cannot be directly processed.

Next, introduce a more convenient processing method

As shown below:

public static void main(String[] args) {
        List<String> stringList = new ArrayList<>();
        stringList.add("a");
        stringList.add("d");
        stringList.add("k");
        System.out.println(String.join(",", stringList));
        List<Object> objectList = new ArrayList<>();
        objectList.add(1L);
        objectList.add(10);
        objectList.add(" Very convenient ");
        System.out.println(objectList.stream().map(Objects::toString).collect(Collectors.joining()));
        System.out.println(objectList.stream().map(Objects::toString).collect(Collectors.joining(",")));
        System.out.println(objectList.stream().map(Objects::toString).collect(Collectors.joining("-")));
        System.out.println(stringList.stream().map(Objects::toString).collect(Collectors.joining("-")));
    }

The List stream function can convert any data type into String, and then use Collectors. joining () method to splice elements in any form, which is really a convenient and simple way.

Stream stream merges strings, splices strings

List<String> strings = Arrays.asList("abc", "", "de", "efg", "abcd", "", "jkl");
String mergeString = strings.stream().filter(string -> !string.isEmpty()).collect(Collectors.joining(","));
System.err.println(" Merge strings  : "+mergeString);

Console output

Merge Strings: abc, de, efg, abcd, jkl

.stream Convert data into an stream stream .filter Filter field Collectors.joining String Connection Collector (String Splicing)