Write a Java Program to Join Two Lists

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Write a Java Program to Join Two Lists

PROGRAM: Java Program to Join Two Lists

/*Java Program to Join Two Lists*/

1: Join Two Lists using addAll()

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

public class JoinLists {

    public static void main(String[] args) {

        List<String> list1 = new ArrayList<String>();
        list1.add("a");

        List<String> list2 = new ArrayList<String>();
        list2.add("b");

        List<String> joined = new ArrayList<String>();

        joined.addAll(list1);
        joined.addAll(list2);

        System.out.println("list1: " + list1);
        System.out.println("list2: " + list2);
        System.out.println("joined: " + joined);

    }
}

2: Join Two Lists using union()

import java.util.ArrayList;
import java.util.List;
import org.apache.commons.collections.ListUtils;

public class JoinLists {

    public static void main(String[] args) {

        List<String> list1 = new ArrayList<String>();
        list1.add("a");

        List<String> list2 = new ArrayList<String>();
        list2.add("b");

        List<String> joined = ListUtils.union(list1, list2);

        System.out.println("list1: " + list1);
        System.out.println("list2: " + list2);
        System.out.println("joined: " + joined);

    }
}

 3: Join Two Lists using stream

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class JoinLists {

    public static void main(String[] args) {

        List<String> list1 = new ArrayList<String>();
        list1.add("a");

        List<String> list2 = new ArrayList<String>();
        list2.add("b");

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

        System.out.println("list1: " + list1);
        System.out.println("list2: " + list2);
        System.out.println("joined: " + joined);

    }
}