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Java

ArrayList Program in Java

Prepbytes

Last Updated on May 5, 2023 by Prepbytes

Arraylist program in java was introduced in Java version 1.2 in 1998.ArrayList is important in Java as it provides array implementation that allows for efficient data storage and manipulation.

Introduction to Arraylist Program in Java

ArrayList program in Java is a resizable dynamic array that can store elements of any data type. It is part of the Java Collections Framework and provides several methods for adding, removing, and accessing elements within the list. Arraylists are useful when the size of the collection is not known in advance or needs to change dynamically. They are implemented using an underlying array that is resized as elements are added or removed and can be used to store both primitive data types and objects.

Arraylist Methods in Java

Here are some common methods of Arraylist in Java:

  • add(): It defines that an element Adds to the end of the Arraylist.
  • add(index, element): Inserts an element at a specific index in the Arraylist.
  • remove(index): Removes the element at a specific index in the Arraylist.
  • get(index): Returns the element at a specific index in the ArrayList.
  • size(): It defines the number of elements in the Arraylist that is returned using the size operator.
  • clear(): Removes all elements from the Arraylist.
  • indexOf(element): It defines the index of the first occurrence of the specified element in the Arraylist that has been returned.
  • lastIndexOf(element): It defines the index of the last occurrence of the specified element in the ArrayList that has returned.
  • contains(element): Returns true if the ArrayList contains the specified element, false otherwise.
  • isEmpty(): Returns true if the Arraylist is empty, false otherwise.
  • toArray(): Converts the Arraylist to an array.
  • sort(): Sorts the Arraylist in ascending order.

Operations Performed in Arraylist Program in Java

Here are some common operations that can be performed with Arraylist program in Java:

  • Adding elements: This can add elements to the end of the ArrayList using the add() method, or insert them at a specific index using the add(index, element) method.

    Example code:

    /* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    public static void main (String[] args) throws java.lang.Exception
    {
        // your code goes here
         ArrayList<String> names = new ArrayList<>();
        names.add("Sharma");
        names.add("Gourav");
        names.add("Deepthi");
        System.out.println(names);
    }
}
     

  • Removing elements: This can remove elements from the ArrayList using the remove() method, which removes the element at a specific index, or the remove(Object) method, which removes the first occurrence of a specific element.

    Example code:

    /* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    public static void main (String[] args) throws java.lang.Exception
    {
        // your code goes here
        ArrayList<String> names = new ArrayList<>();
        names.add("Sharma");
        names.add("Gourav");
        names.add("Deepthi");
        names.remove(1);
        System.out.println(names);
    }
}
     

  • Accessing elements: This can access elements in the ArrayList using the get() method, which returns the element at a specific index.

Example code:

/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    public static void main (String[] args) throws java.lang.Exception
    {
        // your code goes here
        ArrayList<String> names = new ArrayList<>();
        names.add("Sharma");
        names.add("Gourav");
        names.add("Deepthi");
        String name = names.get(1);
        System.out.println(name);
    }
}
 

  • Searching elements: This can search for elements in the ArrayList using the indexOf() method, which returns the index of the first occurrence of a specific element, or the lastIndexOf() method in the index of the last occurrence of a specific element has returned.

    Example code:

    /* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    public static void main (String[] args) throws java.lang.Exception
    {
        // your code goes here
         ArrayList<String> names = new ArrayList<>();
        names.add("Sharma");
        names.add("Gourav");
        names.add("Deepthi");
        int index = names.indexOf("Gourav");
        System.out.println(index);
    }
}
     

  • Sorting elements: This can sort the elements in the ArrayList using the sort() method or the Collections. sort() method.

    Example code:

    /* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    public static void main (String[] args) throws java.lang.Exception
    {
        // your code goes here
        ArrayList<String> names = new ArrayList<>();
        names.add("Sharma");
        names.add("Gourav");
        names.add("Deepthi");
        Collections.sort(names);
        System.out.println(names);
    }
}
     

  • Checking the size and emptiness: This can check the number of elements in the ArrayList using the size() method, or check whether the ArrayList is empty using the isEmpty() method.

  • Converting to array: This can convert the ArrayList to an array using the toArray() method.

  • Iterating over elements: You can iterate over the elements in the ArrayList using a for loop or a for-each loop, or using an iterator or a list iterator.

Example of Arraylist Program in Java

/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    public static void main (String[] args) throws java.lang.Exception
    {
        // your code goes here
         ArrayList<Integer> list = new ArrayList<Integer>();

      // Add some elements to the ArrayList
      list.add(10);
      list.add(20);
      list.add(30);
      list.add(40);

      // Print the ArrayList
      System.out.println("ArrayList: " + list);

      // Remove an element from the ArrayList
      list.remove(2);

      // Print the updated ArrayList
      System.out.println("Updated ArrayList: " + list);

      // Access an element in the ArrayList
      int element = list.get(1);

      // Print the accessed element
      System.out.println("Accessed Element: " + element);

      // Iterate over the elements in the ArrayList
      System.out.print("Iterating over ArrayList: ");
      for (int i = 0; i < list.size(); i++) 
         System.out.print(list.get(i) + " ");
    }
}
 

Explanation of arraylist program in java:
In the Arraylist program in Java, we first create a new ArrayList and add some integer values to it. We then print the ArrayList to the console using the println() method. Then, we remove an element from the ArrayList using the remove() method and print the updated ArrayList to the console. We then access an element in the ArrayList using the get() method and print the accessed element to the console. Finally, we iterate over the elements in the Arraylist program in Java by using a for loop and then printing each element to the console.

Advantages of Arraylist Program in Java

Here are some advantages of Arraylist program in Java:

  • ArrayLists can store elements of any data type.
  • ArrayLists give efficient methods for adding, removing, and accessing elements.
  • It can be easily sorted, searched, and iterated over.
  • It can be serialized and deserialized, allowing for easy storage and retrieval of data.
  • They are easy to use and widely used in Java programming.

Disadvantages of Arraylist Program in Java

Here are some disadvantages of ArrayList in Java:

  • Arraylists have slower performance when elements are frequently added or removed from the middle of the list.
  • Arraylists program in java uses more memory than arrays when storing small numbers of elements.
  • Arraylists program in java does not provide a direct way to sort or search for elements in the list, requiring additional code or the use of Collections class methods.
  • Arraylists program in java is not thread-safe by default, which can cause issues in concurrent programming environments.
  • Arraylists program in java can only store objects and not primitive data types, requiring additional code to convert primitives to objects.

Conclusion
In conclusion, an Arraylist program in Java is a powerful and flexible data structure that provides a dynamic array. It is widely used in Java programming for its ability to store elements of any data type and its efficient methods. They are easy to use, highly efficient, and offer a lot of flexibility, making them an essential tool for Java developers.

Frequently Asked Questions(FAQs)

Q1. Mention the difference between an array and an Arraylist?
Ans: Arrays have a fixed size that cannot be changed, while Arraylists can dynamically resize to accommodate new elements.

Q2. Can Arraylist store elements of different data types?
Ans: Yes, an Arraylist can store elements of any data type.

Q3. How do I add elements to an Arraylist?
Ans: You can use the add() method to add elements to an Arraylist.

Q4. Can I access elements in an Arraylist using an index?
Ans: Yes, you can use the get() method to access elements in an Arraylist using an index.

Q5. How do I iterate over the elements in an Arraylist?
Ans: You can use a for loop or an iterator to iterate over the elements in an Arraylist.

Q6. What is the performance of Arraylist compared to arrays?
Ans: Arraylists have slower performance when elements are frequently added or removed from the middle of the list, but faster performance when elements are accessed randomly.

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