This tutorial shows you how to add elements to arraylist in different ways.
How to add to elements in arraylist java – add(E e)
The below example uses add method from java API to append or add an element to the end of the ArrayList
package com.candidjava.arrayList;
import java.util.ArrayList;
public class ArrayListAdd
{
public static void main(String[] args) {
ArrayList<String> al=new ArrayList<String>();
// add first element to arraylist
al.add("candid");
System.out.println(al); // print arraylist data
// add more elements to arraylist
al.add("mathan");
al.add("antony");
System.out.println(al);
}
}Output
[candid] [candid, mathan, antony]
Add elements to specified positions in arraylist java – add(int index, E element)
package com.candidjava.arrayList;
import java.util.ArrayList;
public class ArrayListAddIndex
{
public static void main(String[] args) {
ArrayList<String> al=new ArrayList<String>();
al.add("candid");
al.add("mathan");
al.add("antony");
System.out.println(al);
// adding element to 1st index position in arraylist
al.add(1, "kumar");
System.out.println("After adding elements in specific index");
System.out.println(al);
}
}Output
[candid, mathan, antony] After adding elements in specific index [candid, kumar, mathan, antony]
How to add arraylist to another arraylist in java – addAll(Collection c)
package com.candidjava.arrayList;
import java.util.ArrayList;
public class ArrayListAddArray
{
public static void main(String[] args) {
ArrayList<String> al1=new ArrayList<String>();
al1.add("candid");
al1.add("mathan");
al1.add("antony");
System.out.println("First arraylist ");
System.out.println(al1);
ArrayList<String> al2=new ArrayList<String>();
al2.add("chennai");
al2.add("tiruchy");
al2.add("madurai");
System.out.println("Second arraylist ");
System.out.println(al2);
// adding arraylist 1 to arraylist 2 using addAll
al2.addAll(al1);
System.out.println("After adding arraylist 1 to arrayList 2");
System.out.println(al2);
}
}Output
First arraylist [candid, mathan, antony] Second arraylist [chennai, tiruchy, madurai] After adding arraylist 1 to arrayList 2 [chennai, tiruchy, madurai, candid, mathan, antony]
How to add array in arraylist in java
package com.candidjava;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class ArrayListAddArray {
public static void main(String[] args) {
String[] names = { "teena", "reena", "meena", "ram", "sam" };
// Using arrays.aslist()
List l = new ArrayList<String>(Arrays.asList(names));
System.out.println("Adding into arraylist using arrays.aslist:");
System.out.println(l);
// Using Collections.addall()
List l1 = new ArrayList<String>();
Collections.addAll(l1, names);
System.out.println("Adding into arraylist using collection.addall:");
System.out.println(l1);
// Adding elements to an already existing array
List l2 = new ArrayList<String>();
Collections.addAll(l2, names);
boolean b = Collections.addAll(l2, "Rahul", "OM", "Prem");
System.out.println("Adding elements into list l2:");
System.out.println(l2);
// Adding elements to array
l1.add("krish");
l1.add("jack");
System.out.println("Adding elements into list l1:");
System.out.println(l1);
}
}Output
Adding into arraylist using arrays.aslist: [teena, reena, meena, ram, sam] Adding into arraylist using collection.addall: [teena, reena, meena, ram, sam] Adding elements into list l2: [teena, reena, meena, ram, sam, Rahul, OM, Prem] Adding elements into list l1: [teena, reena, meena, ram, sam, krish, jack]
How to add int array to arraylist in java
package com.candidjava;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class ArrayListAddIntArray {
public static void main(String[] args) {
Integer[] num = { 12, 33, 44, 55, 66, 77 };
// Using Arrays.aslist
List l = new ArrayList<Integer>(Arrays.asList(num));
System.out.println("adding using arrays.aslist:");
System.out.println(l);
//Using Collections.addall
List l1=new ArrayList<Integer>();
Collections.addAll(l1,num);
System.out.println("adding using collections.addall:");
System.out.println(l1);
//
int[] n=new int[]{22,33,44,55};
List<int[]> l2 = new ArrayList<>();
l2.add(n);
System.out.println(l2.get(0)[0]);
System.out.println(l2.get(0)[1]);
System.out.println(l2.get(0)[2]);
System.out.println(l2.get(0)[3]);
}
}Output
adding using arrays.aslist: [12, 33, 44, 55, 66, 77] adding using collections.addall: [12, 33, 44, 55, 66, 77] 22 33 44 55
How to add class object to arraylist in java
package com.candidjava;
import java.util.ArrayList;
import java.util.Iterator;
class Student {
int rollno;
String name;
int age;
Student(int rollno, String name, int age) {
this.rollno = rollno;
this.name = name;
this.age = age;
}
public int getRollno() {
return rollno;
}
public void setRollno(int rollno) {
this.rollno = rollno;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
public class ArraylistaddObject {
public static void main(String[] args) {
Student s1 = new Student(101, "kavi", 15);
Student s2 = new Student(102, "ram", 15);
Student s3 = new Student(103, "sam", 15);
// Adding objects into array list
ArrayList<Student> al = new ArrayList<Student>();
al.add(s1);
al.add(s2);
al.add(s3);
Iterator itr = al.iterator();
while (itr.hasNext()) {
Student st = (Student) itr.next();
System.out.println(st.getRollno() + " " + st.getName() + " " + st.getAge());
}
}
}
Output
101 kavi 15 102 ram 15 103 sam 15
How to add hashmap values to arraylist in java
package com.candidjava;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Set;
public class ArrayListAddHashMap {
public static void main(String[] args) {
HashMap<Integer, String> hm = new HashMap<>();
hm.put(101, "Remo");
hm.put(102, "Rio");
hm.put(103, "Ram");
//Adding key into arraylist
Set<Integer> ks = hm.keySet();
ArrayList<Integer> al=new ArrayList<Integer>(ks);
System.out.println(al);
//Adding Values into arraylist
Collection<String> value=hm.values();
ArrayList<String> al1=new ArrayList<String>(value);
System.out.println(al1);
}
}
Output
[101, 102, 103] [Remo, Rio, Ram]
