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In this example, we will learn how to merge two lists using the addAll() method and Stream class in Java.
To understand this example, you should be familiar with the followingJava ProgrammingTopic:
import java.util.ArrayList;
import java.util.List;
class Main {
public static void main(String[] args) {
//Create the first list
List<Integer> prime = new ArrayList<>();
prime.add(2);
prime.add(3);
prime.add(5);
System.out.println("First list: "); + prime);
//Create the second list
List<Integer> even = new ArrayList<>();
even.add(4);
even.add(6);
System.out.println("Second list: "); + even);
//Create the merged list
List<Integer> numbers = new ArrayList<>();
numbers.addAll(prime);
numbers.addAll(even);
System.out.println("Merge lists: "); + numbers);
}
}Output Result
First list: [2, 3, 5] Second list: [4, 6] Merge lists: [2, 3, 5, 4, 6]
In the above example, there are two lists named prime and even. Here, we useJava ArrayList addAll()Method, add all elements of prime and even to a new list named numbers.
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
class Main {
public static void main(String[] args) {
// Create the first list
// asList() converts an array to an arraylist
List<Integer> prime = new ArrayList<>(Arrays.asList(2, 3, 5));
System.out.println("First List: "); + prime);
// Create the second list
List<Integer> even = new ArrayList<>(Arrays.asList(4, 6));
System.out.println("Second List: "); + even);
// Convert both lists to streams
Stream<Integer> list1 = prime.stream();
Stream<Integer> list2 = even.stream();
// Merge two streams
Stream<Integer> merged = Stream.concat(list1, list2);
// Convert the merged stream to a list
List<Integer> numbers = merged.collect(Collectors.toList());
System.out.println("Merged List: ", + numbers);
}
}Output Result
First List: [2, 3, 5] Second List: [4, 6] Merged List: [2, 3, 5, 4, 6]
In the above example, we used the Stream class to merge two lists. Here,
stream() - Convert a list to a stream
concat() - Merge two streams
collect(Collectors.toList()) - Convert a stream to a list
For more information about streams, please visitJava Stream Class.