INHERITANCE AND POLYMORPHISM - Introduction to Java Programming: Comprehensive Version - page 436

T ABLE 11.1

Differences and Similarities between Arrays and ArrayList

Operation Array ArrayList

Creating an array/ArrayList String[] a = new String[ 10 ] ArrayList<String> list = new ArrayList<>();

Accessing an element

a[index] list.get(index);

Updating an element a[index] = "London" ; list.set(index, "London" );

Returning size a.length list.size();

Adding a new element list.add( "London" );

Inserting a new element

list.add(index, "London" );

Removing an element list.remove(index);

Removing an element list.remove(Object);

Removing all elements list.clear();

You cannot use the get(index) and set(index, element) methods if the element is not
in the list. It is easy to add, insert, and remove elements in a list, but it is rather complex to
add, insert, and remove elements in an array. You have to write code to manipulate the array
in order to perform these operations. Note that you can sort an array using the java.util.
Arrays.sort(array) method. To sort an array list, use the java.util.Collections.
sort(arraylist) method.
Suppose you want to create an ArrayList for storing integers. Can you use the following
code to create a list?

ArrayList< int > list = new ArrayList<>();

No. This will not work because the elements stored in an ArrayList must be of an object
type. You cannot use a primitive data type such as int to replace a generic type. However,
you can create an ArrayList for storing Integer objects as follows:

ArrayList<Integer> list = new ArrayList<>();

Listing 11.9 gives a program that prompts the user to enter a sequence of numbers and
displays the distinct numbers in the sequence. Assume that the input ends with 0 and 0 is not
counted as a number in the sequence.

L ISTING 11.9

DistinctNumbers.java
1 import java.util.ArrayList;
2 import java.util.Scanner;
3
4 public class DistinctNumbers {
5 public static void main(String[] args) {
6 ArrayList<Integer> list = new ArrayList<>();
7
8 Scanner input = new Scanner(System.in);
9 System.out.print( "Enter integers (input ends with 0): " );
10

create an array list

int value;

11
12 do {
13 value = input.nextInt(); // Read a value from the input
14
15 if (!list.contains(value) && value != 0 )
16 list.add(value); // Add the value if it is not in the list
17 } while (value != 0 );

contained in list?
add to list