Java 8 Streams | Concatenate Two Lists | Stream.concat() with Example

Java 8 Programs

Java 8 Real Time Interview Coding Questions and Answers

We use Stream.concat() to combine two lists and apply:

✔ distinct() to remove duplicates

✔ sorted() with Comparator.reverseOrder()

✔ collect(Collectors.toList()) to store results

package org.practice.basicprgms; import java.util.Arrays; import java.util.Comparator; import java.util.List; import java.util.stream.Collectors; import java.util.stream.Stream; public class ConcatenateListDemo { public static void main(String[] args) { List<String> strList1 = Arrays.asList("Java", "Nodejs", "C"); List<String> strList2 = Arrays.asList("JavaScript", "Angular", "Java", "C"); List<String> combinedList; Stream.concat(strList1.stream(), strList2.stream()) .distinct() .sorted(Comparator.reverseOrder()) .forEach(System.out::println); System.out.println("--------------------------------------"); combinedList = Stream.concat(strList1.stream(), strList2.stream()) .distinct() .sorted(Comparator.reverseOrder()) .collect(Collectors.toList()); System.out.println("Combined Sorted List : "+ combinedList); /* List<Integer> list1 = Arrays.asList(10,40,20,30,50); List<Integer> list2 = Arrays.asList(40,70,60); List<Integer> mergedList; Stream.concat(list1.stream(), list2.stream()) .distinct() .sorted(Comparator.reverseOrder()) .forEach(System.out::println); System.out.println("-----------------------------"); mergedList = Stream.concat(list1.stream(), list2.stream()) .distinct() .sorted(Comparator.reverseOrder()) .collect(Collectors.toList()); System.out.println("Merged Elements : "+ mergedList); */ } }