Java ArrayList, create ArrayList, add elements to ArrayList, return ArrayList size, remove elements of ArrayList, and clear all elements of the ArrayList.
Java Array is Static Data Structure and ArrayList is Dynamic Data Structure
Array versus ArrayList in Java
Array is Static (its size is fixed), ArrayList is Dynamic….
Java Array Example:
int [] a= new a[4];
a[0]=10;
a[1]=20;
a[2]=30;
a[3]=40;
a[4]=50; //Error
ArrayList is Dynamic and you can add or remove elements….
Note: ArrayList is a predefined class that we have to import from java.util package
Create an ArrayList object called “myTools: that will store strings:
import java.util.ArrayList; // import the ArrayList class
ArrayList<String> myTools = new ArrayList<String>(); // Create an ArrayList object
Add Items
ArrayList <String> myTool = new ArrayList<> ();
myTools.add(“Selenium”);
myTools.add(“UFT”);
myTools.add(“JMeter”);
Access an Item
To access an element in the ArrayList, use the get() method and refer to the index number:
Example
myTools.get(0);
Change an Item
To modify an element, use the set() method and refer to the index number:
Example
myTools.set(0, “Appium”);
Remove an Item
To remove an element, use the remove() method and refer to the index number:
Example:
myTools.remove(1);
Remove all Items
To remove all items, use the clear() method and refer to the index number:
Example:
myTools.remove(1);
ArrayList Size
To find out how many elements an ArrayList have, use the size method:
Example:
myTools.size();
Examples:
1. Create Integer type ArrayList and conduct operations
ArrayList <Integer> abc = new ArrayList <> ();
//Add elements to ArrayList
abc.add(100);
abc.add(200);
abc.add(300);
//Return & Print an Array Element
int val=abc.get(2);
System.out.println(val);//300
//Print an Array Element
System.out.println(abc.get(1));//200
//Return & Print Size of the ArrayList
int x = abc.size();
System.out.println(x);//3
//Print Size of the ArrayList
System.out.println(abc.size());//3
//Remove an element
System.out.println(abc.get(1));//200
abc.remove(1);
System.out.println(abc.get(1));//300
System.out.println(abc.size());//2
abc.add(400);
abc.add(500);
System.out.println(abc.size());//4
//Check the existence of Elements
System.out.println(abc.contains(200));//false
System.out.println(abc.contains(300));//true
//Remove all elements
System.out.println(abc.size());//4
abc.clear();
System.out.println(abc.size());//0
abc.add(123);
abc.add(234);
System.out.println(abc.size());//2
2. Create String type ArrayList
ArrayList <String> myTool = new ArrayList<> ();
myTool.add(“Selenium”);
myTool.add(“UFT”);
myTool.add(“JMeter”);
String val = myTool.get(1);
System.out.println(val);//UFT
int x= myTool.size();
System.out.println(x);//3
boolean y=myTool.contains(“JMeter”);
System.out.println(y);//true
myTool.clear();
System.out.println(myTool.size());//0
3. Create Character type ArrayList
ArrayList <Character> xyz = new ArrayList<> ();
xyz.add(‘A’);
xyz.add(‘3’);
xyz.add(‘&’);
System.out.println(xyz.size());//3
char a= xyz.get(2);
System.out.println(a);//&