What is the best way to get the result through Java8 function?

Ashish Goel :

I need to filter elements and then sort based on certain column. Post that I would need to find the unique entries based on combination of columns. Since it is file processing, pipe(|) is used as delimiter to denote the column value.

String s1= "12|Thor|Asgaurd|1000000|Avenger|Active"
String s2= "234|Iron man|New York|9999999|Avenger|Active"
String s3= "420|Loki|Asgaurd|||Inactive"
String s4= "12|Thor|Asgaurd Bank|1000000|Avenger HQ|Active"

Data first needs to be filtered based on the Active/Inactive status. Then it needs to be sorted based on 4th column. Lastly, the uniqueness needs to be maintained by combining column 1,2,3.

Expected Output =

"234|Iron man|New York|9999999|Avenger|Active"
"12|Thor|Asgaurd|1000000|Avenger|Active"

Samuel Philipp :

First of all you should create an Object which represents your String data. Something like this:

public class MyObject {
    private int id;
    private String name;
    private String location;
    private Integer value;
    private String category;
    private String state;

    public MyObject(String entry) {
        String[] parts = entry.split("\\|");
        if (parts.length != 6) {
            throw new IllegalArgumentException("entry has not 6 parts");
        }
        id = Integer.parseInt(parts[0]);
        name = parts[1];
        location = parts[2];
        try {
            value = Integer.parseInt(parts[3]);
        } catch (NumberFormatException ignored) {
        }
        category = parts[4];
        state = parts[5];
    }

    // getters

    @Override
    public String toString() {
        return String.join("|", String.valueOf(id), name, location, String.valueOf(value), category, state);
    }
}

With this you can create a Stream of objects from your Strings and to the filter, sort and distinct operations afterwards:

Collection<MyObject> result = Stream.of(s1, s2, s3, s4)
        .map(MyObject::new)
        .filter(o -> "Active".equals(o.getState()))
        .sorted(Comparator.comparing(MyObject::getValue).reversed())
        .collect(Collectors.toMap(o -> Arrays.asList(o.getId(), o.getName()), 
                Function.identity(), (o1, o2) -> o1, LinkedHashMap::new))
        .values();

result.forEach(System.out::println);

After the map operation you filter the values by state and sort them by column 4 (value in my case). At the end you collect all the values in a map for the distinct operation. Add all values you need distinction for to the Arrays.asList(). As values the map takes all the original values (Function.identity()). For duplicates we keep the first value ((o1, o2) -> o1) and we are using a LinkedHashMap to keep the order of the items. At the end wee use only the values of the map.

If you need a List instead of a Collection use new ArrayList(result).

The result will be this:

234|Iron man|New York|9999999|Avenger|Active
12|Thor|Asgaurd|1000000|Avenger|Active