In this article, we will discuss how to reverse the contents of ArrayList using Collections class’s utility reverse() method
1. To reverse ArrayList contents :
Method signature:
public static void reverse(List list);
- This method is used to reverse the order of ArrayList contents
- i.e.; reverse-order of insertion-order
ReverseArrayListContents.java
package in.bench.resources.java.collections;
import java.util.ArrayList;
import java.util.Collections;
public class ReverseArrayListContents {
public static void main(String[] args) {
// creating ArrayList object of type String
ArrayList<String> companies = new ArrayList<String>();
// adding elements to ArrayList object
companies.add("LinkedIn");
companies.add("Amazon");
companies.add("Google");
companies.add("Apple");
companies.add("Facebook");
companies.add("Oracle");
companies.add("Microsoft");
// Iterating using enhanced for-loop
System.out.println("Insertion Order: Iterating ArrayList\n");
for(String company : companies) {
System.out.println(company);
}
// to reverse ArrayList contents
Collections.reverse(companies);
// reverse order of ArrayList contents
System.out.println("\n\n\nReverse Order: Iterating ArrayList\n");
for(String company : companies) {
System.out.println(company);
}
}
}
Output:
Insertion Order: Iterating ArrayList
LinkedIn
Amazon
Google
Apple
Facebook
Oracle
Microsoft
Reverse Order: Iterating ArrayList
Microsoft
Oracle
Facebook
Apple
Google
Amazon
LinkedIn
From above example, ArrayList
- allows duplicate elements
- null object is allowed
- while iterating insertion-order is maintained
Related Articles:
- Java – Creating ArrayList using nCopies method of Collections class
- Java – How to get size or length of an ArrayList ?
- Java – Adding element to ArrayList at specified index position
- Java – Remove element from ArrayList at specified index position
- Java – How to delete a element and delete all elements of an ArrayList ?
- Java- How to get sublist from ArrayList ?
- Java – How to check whether particular element is present in ArrayList ?
- Java – Comparing two ArrayList objects using containsAll() method
- Java – Adding one ArrayList to another ArrayList using addAll() method
- Java – Replacing ArrayList element with new value using set() method
- Java – Various ways to iterate through ArrayList
- Java – How to reverse ArrayList contents ?
- Java – Remove duplicate elements from ArrayList
- Java – How to remove duplicate elements of ArrayList maintaining insertion-order ?
References:
- https://docs.oracle.com/javase/tutorial/collections/intro/
- https://docs.oracle.com/javase/tutorial/collections/interfaces/collection.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Collection.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Enumeration.html
- https://docs.oracle.com/javase/7/docs/api/java/util/Iterator.html
- https://docs.oracle.com/javase/7/docs/api/java/util/ListIterator.html
Happy Coding !!
Happy Learning !!
