November 16, 2024 - import java.util.*; public class GFG { public static void main(String args[]) { // Get the ArrayList1 ArrayList<String> list1 = new ArrayList<String>(); // Populate the ArrayList list1.add("Geeks"); list1.add("for"); list1.add("Geeks"); // Get the ArrayList2 ArrayList<String> list2 = new ArrayList<String>(); list2.add("GeeksForGeeks"); list2.add("A Computer Science Portal"); // Join the ArrayLists // using Collection.addAll() method list1.addAll(list2); // Print the joined ArrayList System.out.println(list1); } }

February 24, 2016 - In this example we are merging two ArrayLists in one single ArrayList and then displaying the elements of final List. package beginnersbook.com; import java.util.ArrayList; public class Details { public static void main(String [] args) { //First ArrayList ArrayList<String> arraylist1=new ArrayList<String>(); arraylist1.add("AL1: E1"); arraylist1.add("AL1: E2"); arraylist1.add("AL1: E3"); //Second ArrayList ArrayList<String> arraylist2=new ArrayList<String>(); arraylist2.add("AL2: E1"); arraylist2.add("AL2: E2"); arraylist2.add("AL2: E3"); //New ArrayList ArrayList<String> al= new ArrayList<String>(); al.addAll(arraylist1); al.addAll(arraylist2); //Displaying elements of the joined ArrayList for(String temp: al){ System.out.println(temp); } } }

January 8, 2025 - It always returns a concatenated string of elements joined by the delimiter. import java.util.ArrayList; class Main { public static void main(String[] args) { ArrayList<String> arrayOfStrings = new ArrayList<>(); arrayOfStrings.add("Concatenating"); arrayOfStrings.add("the"); arrayOfStrings.add("array"); arrayOfStrings.add("list"); arrayOfStrings.add("elements"); arrayOfStrings.add("with"); arrayOfStrings.add("space"); arrayOfStrings.add("as"); arrayOfStrings.add("delimiter"); // joining arrayList with space between them as delimiter String joinedStr = String.join(" ", arrayOfStrings); System.out.println(joinedStr); } } Concatenating the array list elements with space as delimiter ·

March 14, 2024 - import java.util.ArrayList; class ...tln("ArrayList: " + languages); // convert the arraylist into a string String arraylist = String.join(", ", languages); System.out.println("String: " + arraylist); } }...

We can also join two ArrayLists by using the flatMap() method and distinct() method by following the code below: import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.List; import java.util.strea...

September 25, 2018 - List<String> feed = new ArrayList<>(List.of("post3", "post4")); feed.addAll(0, List.of("post1", "post2")); List<String> newestFirst = feed; // [post1, post2, post3, post4] The Stream.concat() method joins two streams into one, so Stream.con...

Here is a simple Java program to demonstrate how to use the addAll() method of Collection interface to join elements of two array lists in Java. In this program, we have two ArrayList objects, first contains some UK-based banks like Barclays, ...

December 24, 2020 - Call String.join() method and pass the delimiter string delimiter followed by the ArrayList<String> arrayList.

For a simple string ArrayList, String.join is the best method to use.

August 1, 2023 - import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class Main { public static void main(String args[]) { String a[] = { "A", "E", "I" }; String b[] = { "O", "U" }; List list = new ArrayList(Arrays.asList(a)); list.addAll(Arrays.asList(b)); Object[] c = list.toArray(); System.out.println(Arrays.toString(c)); } } The above code sample will produce the following result.

April 4, 2025 - In the following example we first join within each nested Collection and then we join the result of each of them: @Test public void whenConvertNestedCollectionToString_thenConverted() { Collection<List<String>> nested = new ArrayList<>(); nested.add(Arrays.asList("Dog", "Cat")); nested.add(Arrays.asList("Cow", "Pig")); String result = nested.stream().map( nextList -> nextList.stream() .collect(Collectors.joining("-"))) .collect(Collectors.joining("; ")); assertEquals(result, "Dog-Cat; Cow-Pig"); }

December 27, 2024 - Use the join() method to concatenate the array’s elements.

July 23, 2025 - We can convert ArrayList to a ... with a supplied prefix and ending with a supplied suffix. The join() method of the String class can be used to construct the same....

November 29, 2018 - package com.mkyong; import java.util.Arrays; import java.util.List; public class JavaStringExample1 { public static void main(String[] args) { List<String> list = Arrays.asList("a","b","c"); String result = String.join(",", list); System.out.println(result); } }

May 21, 2025 - Write a Java program to join two array lists. ... import java.util.ArrayList; import java.util.Collections; public class Exercise15 { public static void main(String[] args) { ArrayList<String> c1= new ArrayList<String>(); c1.add("Red"); c1.add("Green"); c1.add("Black"); c1.add("White"); c1.add("Pink"); System.out.println("List of first array: " + c1); ArrayList<String> c2= new ArrayList<String>(); c2.add("Red"); c2.add("Green"); c2.add("Black"); c2.add("Pink"); System.out.println("List of second array: " + c2); // Let join above two list ArrayList<String> a = new ArrayList<String>(); a.addAll(c1); a.addAll(c2); System.out.println("New array: " + a); } }

February 8, 2016 - this is a great post about how to join array thanks · Reply Helpful Report Spam or advertising Abusive or offensive Off topic · D · della pramukti raharjo · March 24, 2016 at 3:36 pm · import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class JoinArray { public static void main(String[] args) { String[] s1 = new String[] { “a”, “b”, “c” }; String[] s2 = new String[] { “d”, “e”, “f” }; List listString = new ArrayList(); for (String s : s1) listString.add(s); for (String s : s2) listString.add(s); String[] s3 = listString.toArray(new String[0]); System.out.println(“Value List String :” + listString.toString()); System.out.println(“Value join array :” + Arrays.toString(s3)); } } Reply Helpful Report Spam or advertising Abusive or offensive Off topic ·

July 30, 2026 - If our elements in the List aren’t subclasses of CharSequence, we can first convert the List to a List<String>, and then pass it to String.join():

Another way of merging ArrayList is using Apache Commons Collection, Apart from several goodies, like creating a union of Set in Java, it provides a ListUtils class with a union method, which can be used to create a union of two List in Java. The result of the previous operation and is the same, It also preservers the order and appends elements of the second List after elements of the first List. Here is full code example of joining two List in Java.