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How to remove an element from ArrayList in Java?

  • Difficulty Level : Easy
  • Last Updated : 16 Sep, 2021

ArrayList is a part of collection framework and is present in java.util package. It provides us with dynamic arrays in Java. Though, it may be slower than standard arrays but can be helpful in programs where lots of manipulation in the array is needed. This class is found in java.util package. With the introduction and upgradations in java versions, newer methods are being available as if we do see from Java8 perceptive lambda expressions and streams concepts were not available before it as it been introduced in java version8, so do we have more ways to operate over Arraylist to perform operations. Here we will be discussing a way to remove an element from an ArrayList.

While removing elements from ArrayList there can either we are operating to remove elements over indexes or via values been there in an ArrayList. We will be discussing both ways via interpreting through a clean java program. 

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Methods:

There are 3 ways to remove an element from ArrayList as listed which later on will be revealed as follows:



  1. Using remove() method by indexes(default)
  2. Using remove() method by values
  3. Using remove() method over iterators

Note: It is not recommended to use ArrayList.remove() when iterating over elements. 

Method 1: Using remove() method by indexes

It is a default method as soon as we do use any method over data structure it is basically operating over indexes only so whenever we do use remove() method we are basically removing elements from indicies from an ArrayList.

ArrayList class provides two overloaded remove() methods. 

Let us figure out with the help of examples been provided below as follows:

Example:

Java




// Java program to Remove Elements from ArrayList
// Using remove() method by indicies
 
// Importing required classes
import java.util.ArrayList;
import java.util.List;
 
// Main class
public class GFG {
    // Main driver method
    public static void main(String[] args)
    {
        // Creating an object of List interface with
        // reference to ArrayList class
        List<Integer> al = new ArrayList<>();
 
        // Adding elements to our ArrayList
        // using add() method
        al.add(10);
        al.add(20);
        al.add(30);
        al.add(1);
        al.add(2);
 
        // Printing the current ArrayList
        System.out.println(al);
 
        // This makes a call to remove(int) and
        // removes element 20
        al.remove(1);
 
        // Now element 30 is moved one position back
        // So element 30 is removed this time
        al.remove(1);
 
        // Printing the updated ArrayList
        System.out.println(al);
    }
}
Output
[10, 20, 30, 1, 2]
[10, 1, 2]

Now we have seen removing elements in an ArrayList via indexes above, now let us see that the passed parameter is considered an index. How to remove elements by value. 



Method 2: Using remove() method by values

Example:

Java




// Java program to Remove Elements from ArrayList
// Using remove() method by values
 
// Importing required classes
import java.util.ArrayList;
import java.util.List;
 
// Main class
public class GFG {
    // Main driver method
    public static void main(String[] args)
    {
        // Creating an object of List interface with
        // reference to ArrayList
        List<Integer> al = new ArrayList<>();
 
        // Adding elements to ArrayList class
        // using add() method
        al.add(10);
        al.add(20);
        al.add(30);
        al.add(1);
        al.add(2);
 
        // Printing the current ArrayList
        System.out.println(al);
 
        // This makes a call to remove(Object) and
        // removes element 1
        al.remove(new Integer(1));
 
        // This makes a call to remove(Object) and
        // removes element 2
        al.remove(new Integer(2));
 
        // Printing the modified ArrayList
        System.out.println(al);
    }
}

Output : 

[10, 20, 30,1 ,2]
[10, 20, 30]

Note: It is not recommended to use ArrayList.remove() when iterating over elements. 

Method 3: Using Iterator.remove() method 

This may lead to ConcurrentModificationException  When iterating over elements, it is recommended to use Iterator.remove() method. 

Example:

Java




// Java program to demonstrate working of
// Iterator.remove() on an integer arraylist
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
 
public class GFG {
 
    // Main driver method
    public static void main(String[] args)
    {
        // Creating an ArrayList
        List<Integer> al = new ArrayList<>();
 
        // Adding elements to our ArrayList
        // using add() method
        al.add(10);
        al.add(20);
        al.add(30);
        al.add(1);
        al.add(2);
 
        // Printing the current ArrayList
        System.out.println(al);
 
        // Creating iterator object
        Iterator itr = al.iterator();
 
        // Holds true till there is sibgle element
        // remaining in the object
        while (itr.hasNext()) {
 
            // Remove elements smaller than 10 using
            // Iterator.remove()
            int x = (Integer)itr.next();
            if (x < 10)
                itr.remove();
        }
 
        // Printing the updated ArrayList
        System.out.print(al);
    }
}
Output
[10, 20, 30, 1, 2]
[10, 20, 30]

This article is contributed by Nitsdheerendra. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.




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