Overview
In this tutorial, we show you how to join two
ArrayList in Java. There are three Ways to join two ArrayList. Using the
addAll() method of collections, for loop with an
ArrayList and
Apache Commons Collections library.
Join two ArrayList using ArrayList.addAll() method
package com.jackrutorial;
import java.util.ArrayList;
import java.util.List;
public class JoinArrayListExample1 {
public static void main(String[] args) {
List springData = new ArrayList();
springData.add("Spring Data Aerospike");
springData.add("Spring Data ArangoDB");
springData.add("Spring Data Couchbase");
List springSecurity = new ArrayList();
springSecurity.add("Spring Security Kerberos");
springSecurity.add("Spring Security OAuth");
springSecurity.add("Spring Security SAML");
List springProject = new ArrayList();
springProject.addAll(springData);
springProject.addAll(springSecurity);
System.out.println("List Spring Project: " + springProject);
}
}
Output
List Spring Project: [Spring Data Aerospike, Spring Data ArangoDB, Spring Data Couchbase, Spring Security Kerberos, Spring Security OAuth, Spring Security SAML]
Join two ArrayList using for loop with an ArrayList
package com.jackrutorial;
import java.util.ArrayList;
import java.util.List;
public class JoinArrayListExample2 {
public static void main(String[] args) {
List springData = new ArrayList();
springData.add("Spring Data Aerospike");
springData.add("Spring Data ArangoDB");
springData.add("Spring Data Couchbase");
List springSecurity = new ArrayList();
springSecurity.add("Spring Security Kerberos");
springSecurity.add("Spring Security OAuth");
springSecurity.add("Spring Security SAML");
List springProject = new ArrayList();
for(String tmp : springData) {
springProject.add(tmp);
}
for(String tmp : springSecurity) {
springProject.add(tmp);
}
System.out.println("List Spring Project: " + springProject);
}
}
Output
List Spring Project: [Spring Data Aerospike, Spring Data ArangoDB, Spring Data Couchbase, Spring Security Kerberos, Spring Security OAuth, Spring Security SAML]
Join two ArrayList with Apache Commons Collections library
We use the
Apache commons-collections library (ex: commons-collections-3.0.jar) with
ListUtils.union() method to joining two lists into a single ArrayList.
package com.jackrutorial;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.collections.ListUtils;
public class JoinArrayListExample3 {
public static void main(String[] args) {
List springData = new ArrayList();
springData.add("Spring Data Aerospike");
springData.add("Spring Data ArangoDB");
springData.add("Spring Data Couchbase");
List springSecurity = new ArrayList();
springSecurity.add("Spring Security Kerberos");
springSecurity.add("Spring Security OAuth");
springSecurity.add("Spring Security SAML");
List springProject = ListUtils.union(springData, springSecurity);
System.out.println("List Spring Project: " + springProject);
}
}
Output
List Spring Project: [Spring Data Aerospike, Spring Data ArangoDB, Spring Data Couchbase, Spring Security Kerberos, Spring Security OAuth, Spring Security SAML]
