Question

How to merge two lists in Java

Answer 1

import java.util.ArrayList;
import java.util.List;

public class MyClass {
    public static void main(String args[]) {
        List<String> list1 = new ArrayList<>();
        list1.add("java");
        list1.add("c");
        list1.add("c++");
        
        List<String> list2 = new ArrayList<>();
        list2.add("python");
        list2.add("c#");
        list2.add("php");
        list2.add("javascript");


        List<String> list1_2 = new ArrayList<>();
        list1_2.addAll(list1);
        list1_2.addAll(list2);

        System.out.println(list1_2);
    }
}
 
 
 
 
/*
run:
   
[java, c, c++, python, c#, php, javascript]
 
*/

 

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Answer 2

import java.util.ArrayList;
import java.util.List;
import java.util.stream.*;

public class MyClass {
    public static void main(String args[]) {
        List<String> list1 = new ArrayList<>();
        list1.add("java");
        list1.add("c");
        list1.add("c++");
        
        List<String> list2 = new ArrayList<>();
        list2.add("python");
        list2.add("c#");
        list2.add("php");
        list2.add("javascript");


        List<String> list1_2 = Stream.concat(list1.stream(), list2.stream()).collect(Collectors.toList());

        System.out.println(list1_2);
    }
}
 
 
 
 
/*
run:
   
[java, c, c++, python, c#, php, javascript]
 
*/

 

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