✓ ArrayList implements List, Collection, Cloneable, Serializable, Iterable and randomaccess interfaces.
✓ ArrayList was introduced in JDK 1.2 version.
✓ The underlying data structure for the ArrayList is resizable array.
✓ The initial capacity of ArrayList is 10.
ex:
import java.util.*;
public class ArrayList {
public static void main(String[] args) {
ArrayList<String> a = new ArrayList<String>();
a.add("steve");
a.add("tom");
a.add("cat");
a.add("jerry");
//display elements
System.out.print(a+" "); //output : steve tom cat jerry
//Add vijay at 3rd position
a.add(2,"vijay");
System.out.print(a+" ");// output : steve tom vijay cat jerry
//To update the value at particular index
a.set(0,"rosy");
System.out.print(a+" ");// output : rosy tom vijay cat jerry
//To remove the element at particular index
a.remove(1);
System.out.print(a+" ");// output : rosy vijay cat jerry
//using for each loop we can display the results
for(String s : a) {
System.out.println(s);
}
//To display the size of ArrayList
System.out.print(a.size());//output : 4
//To sort the elements in Alphabetical order
Collections.sort(a);
for(String s : a) {
System.out.print(s+" ");// output : cat jerry rosy vijay
}
}
}
Note:
✓With in the collections no primitive values are allowed.
✓ If you try to add primitive values then that will be converted into its corresponding wrapper class object and address of object will be stored within the given collection.
✓Collection class have some inbuilt methods like sort() and search(). By using this class we can sort elements present in ArrayList.