Java – Programs using ArrayList Methods

Program to display ArrayList and its size:

add() method is used to append element to the list.
size() method returns the length of list.

import java.util.*;
class Code
{
            public static void main(String[] args) {
                        List<Integer> list = new ArrayList<Integer>();
                        list.add(10);
                        list.add(20);
                        list.add(30);
                        list.add(40);
                        list.add(50);
                        System.out.println(“List is : ” + list);
                        System.out.println(“Size is : ” + list.size());
            }
}

Program to check the list is empty or not:

isEmpty() method returns true if the list doesn’t contains elements else returns false

import java.util.*;
class Code
{
            public static void main(String[] args) {
                        List<Integer> list = new ArrayList<Integer>();
                        if(list.isEmpty())
                                    System.out.println(“List is empty”);
                        else
                                    System.out.println(“List contains elements”);
            }
}

Program to display the element of specified index:

get(int index) returns the element of specified index.

import java.util.*;
class Code
{
            public static void main(String[] args){
                        Scanner sc = new Scanner(System.in);
                        List<Integer> list = new ArrayList<Integer>();
                        for (int i=10 ; i<=50 ; i+=10){
                                    list.add(i);
                        }
                        System.out.println(“List is : ” + list);
                        System.out.println(“Enter index to display value : “);
                        int loc = sc.nextInt();
                        System.out.println(“Element @ index-” + loc + ” is : ” + list.get(loc));
            }
}

We specify the error message – if the index value is not present:

if(loc>=0 && loc<=list.size()-1)
{
System.out.println(list.get(loc));
}
else
{
System.out.println(“Invalid index”);
}

try
{
System.out.println(list.get(loc));
}
catch(IndexOutOfBoundsException e)
{
System.out.println(“Invalid index”);
}

Insert element into specified index: add(int index, E e) method is used to insert element into specified index.

Instructions to code:

Create ArrayList with 5 elements 10, 20, 30, 40, 50
Read index to insert.
Check whether the index is present or not
If the index is present, then read the value and insert.
If the index is not present, display Error message.

import java.util.*;
class Code
{
            public static void main(String[] args) {
                        Scanner sc = new Scanner(System.in);
                        List<Integer> list = new ArrayList<Integer>();
                        list.add(10);
                        list.add(20);
                        list.add(30);
                        list.add(40);
                        list.add(50);
                        System.out.println(“List is : ” + list);
                        System.out.print(“Enter index to insert : “);
                        int loc = sc.nextInt();
                        if(loc>=0 && loc<list.size()){
                                    System.out.print(“Enter element to insert : “);
                                    int ele = sc.nextInt();
                                    list.add(loc, ele);
                                    System.out.println(“List is : ” + list);
                        }
                        else{
                                    System.out.println(“Invalid index”);
                        }
            }
}

Program to remove all elements from the list: clear() method removes all elements from the list.

Instructions to code:

Create list with 5 elements.
Display – List is not empty
Remove all elements using clear() method
Display – List is empty.

import java.util.*;
class Code
{
            public static void main(String[] args){
                        List<Integer> list = new ArrayList<Integer>();
                        for(int i=1 ; i<=5 ; i++)
                                    list.add(i);

                        System.out.println(“List is : ” + list);
                        if(list.isEmpty())
                                    System.out.println(“List is empty”);
                        else
                                    System.out.println(“List is not empty”);

                        list.clear();
                        System.out.println(“List is : ” + list);
                        if(list.isEmpty())
                                    System.out.println(“List is empty”);
                        else
                                    System.out.println(“List is not empty”);
            }
}

Program to remove index element: remove(int index) method removes element of specified index.

Instructions to code:

Create list with elements
Read index value.
If the index is valid – remove the element and display list
If the index is not valid – display error message.

import java.util.*;
class Code
{
            public static void main(String[] args) {
                        Scanner sc = new Scanner(System.in);
                        List<Integer> list = new ArrayList<Integer>();
                        for(int i=1 ; i<=5 ; i++){
                                    list.add(i);
                        }
                        System.out.println(“List is : ” + list);

                        System.out.print(“Enter index to remove : “);
                        int loc = sc.nextInt();
                        if(loc>=0 && loc<list.size()){
                                    list.remove(loc);
                                    System.out.println(“List is : ” + list);
                        }
                        else{
                                    System.out.println(“Error : No such index to remove”);
                        }
            }
}

Program to check whether the list contains element or not: contains() method returns true if the list has specified element.

import java.util.*;
class Code
{
            public static void main(String[] args){
                        Scanner sc = new Scanner(System.in);
                        List<Integer> list = new ArrayList<Integer>();
                        for(int i=1 ; i<=5 ; i++)
                                    list.add(i);
                        System.out.println(“List is : ” + list);
                        System.out.print(“Enter element to check in list : “);
                        int ele = sc.nextInt();
                        if(list.contains(ele))
                                    System.out.println(“Yes element is present in list”);
                        else
                                    System.out.println(“No such element in list”);
            }
}

Program display the index value of element: indexOf() method returns index of specified element. It returns -1 if no such element in the list.

import java.util.*;
class Code
{
            public static void main(String[] args) {
                        Scanner sc = new Scanner(System.in);
                        List<Integer> list = new ArrayList<Integer>();
                        for(int i=1 ; i<=5 ; i++)
                                    list.add(i);
                        System.out.println(“List is : ” + list);
                        System.out.print(“Enter element to find index value : “);
                        int ele = sc.nextInt();
                        int index = list.indexOf(ele);
                        if(index!=-1)
                                    System.out.println(“Index value is : ” + index);
                        else
                                    System.out.println(“No such element in list”);
            }
}

Program to replace the existing value: set(int index, E e) method replace the index element with specified element.

Instructions to code:

Create ArrayList with elements.
Read the element to replace
Check the element is present or not in the list using contains() method.
If the element is present,
- Read the new element to replace with.
If the element is not present,
- Display error message.

import java.util.*;
class Code
{
            public static void main(String[] args) {
                        Scanner sc = new Scanner(System.in);
                        List<Integer> list = new ArrayList<Integer>();
                        for(int i=1 ; i<=5 ; i++){
                                    list.add(i);
                        }
                        System.out.println(“List is : ” + list);
                        System.out.print(“Enter element to replace : “);
                        int x = sc.nextInt();
                        if(list.contains(x)) {
                                    System.out.print(“Enter new element : “);
                                    int y = sc.nextInt();

                                    int loc = list.indexOf(x);
                                    list.set(loc, y);
                                    System.out.println(“Updated list : ” + list);
                        }
                        else
                                    System.out.println(“No such element in list”);
            }
}

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