[Turn] to merge the two and remove duplicates List

 Original: https: //my.oschina.net/jack90john/blog/1493170

Many times the work will need to merge two List and remove duplicate content. This is a very simple operation, here is mainly the record about to complete this operation by using Stream.

    Before java8 more conventional approach is to add two to a Set List, because the content Set of unrepeatable, it will automatically go heavy, then turn the Set List, the following code:

        Set<String> set = new HashSet<>(listA);
        set.addAll(listB);
        List<String> list = new ArrayList<>(set);
        System.out.println(list);

 

list after the merger and to do so is the result of heavy.

    After java8 happens, we have a more convenient and efficient approach is to help us complete this operation by Stream, code is as follows:

List<String> collect = Stream.of(listA, listB)
                .flatMap(Collection::stream)
                .distinct()
                .collect(Collectors.toList());

 

The results thus obtained final results we want, you can clearly see the finished code via Stream looks more simple and smooth.

Tips: If you want to merge is subject Please note that override equals and hashcode methods.

Attachment:

Complete code, for reference.

import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Combine {

    public static void main(String[] args) {

        String[] arr1 = {"a", "b", "c", "d", "e", "f"};
        List<String> listA = new ArrayList<>(Arrays.asList(arr1));

        String[] arr2 = {"d", "e", "f", "g", "h"};
        List<String> listB = new ArrayList<>(Arrays.asList(arr2));

        Set<String> set = new HashSet<>(listA);
        set.addAll(listB);
        List<String> list = new ArrayList<>(set);
        System.out.println(list);

        List<String> collect = Stream.of(listA, listB)
                .flatMap(Collection::stream)
                .distinct()
                .collect(Collectors.toList());
        System.out.println(collect);
    }

}