How to iterate through Java List? This tutorial demonstrates the use of ArrayList, Iterator and a List.
There are 7 ways you can iterate through List.
- Simple For loop
- Enhanced For loop
- Iterator
- ListIterator
- While loop
- Iterable.forEach() util
- Stream.forEach() util
Java Example:
You need JDK 13 to run below program as point-5
above uses stream()
util.
void java.util.stream.Stream.forEach
(Consumer<? super String> action) performs an action for each element of this stream.
package crunchify.com.tutorials; import java.util.*; /** * @author Crunchify.com * How to iterate through Java List? Seven (7) ways to Iterate Through Loop in Java. * 1. Simple For loop * 2. Enhanced For loop * 3. Iterator * 4. ListIterator * 5. While loop * 6. Iterable.forEach() util * 7. Stream.forEach() util */ public class CrunchifyIterateThroughList { public static void main(String[] argv) { // create list List<String> crunchifyList = new ArrayList<String>(); // add 4 different values to list crunchifyList.add("Facebook"); crunchifyList.add("Paypal"); crunchifyList.add("Google"); crunchifyList.add("Yahoo"); // Other way to define list is - we will not use this list :) List<String> crunchifyListNew = Arrays.asList("Facebook", "Paypal", "Google", "Yahoo"); // Simple For loop System.out.println("==============> 1. Simple For loop Example."); for (int i = 0; i < crunchifyList.size(); i++) { System.out.println(crunchifyList.get(i)); } // New Enhanced For loop System.out.println("\n==============> 2. New Enhanced For loop Example.."); for (String temp : crunchifyList) { System.out.println(temp); } // Iterator - Returns an iterator over the elements in this list in proper sequence. System.out.println("\n==============> 3. Iterator Example..."); Iterator<String> crunchifyIterator = crunchifyList.iterator(); while (crunchifyIterator.hasNext()) { System.out.println(crunchifyIterator.next()); } // ListIterator - traverse a list of elements in either forward or backward order // An iterator for lists that allows the programmer to traverse the list in either direction, modify the list during iteration, // and obtain the iterator's current position in the list. System.out.println("\n==============> 4. ListIterator Example..."); ListIterator<String> crunchifyListIterator = crunchifyList.listIterator(); while (crunchifyListIterator.hasNext()) { System.out.println(crunchifyListIterator.next()); } // while loop System.out.println("\n==============> 5. While Loop Example...."); int i = 0; while (i < crunchifyList.size()) { System.out.println(crunchifyList.get(i)); i++; } // Iterable.forEach() util: Returns a sequential Stream with this collection as its source System.out.println("\n==============> 6. Iterable.forEach() Example...."); crunchifyList.forEach((temp) -> { System.out.println(temp); }); // collection Stream.forEach() util: Returns a sequential Stream with this collection as its source System.out.println("\n==============> 7. Stream.forEach() Example...."); crunchifyList.stream().forEach((crunchifyTemp) -> System.out.println(crunchifyTemp)); } }
Output:
==============> 1. Simple For loop Example. Facebook Paypal Google Yahoo ==============> 2. New Enhanced For loop Example.. Facebook Paypal Google Yahoo ==============> 3. Iterator Example... Facebook Paypal Google Yahoo ==============> 4. ListIterator Example... Facebook Paypal Google Yahoo ==============> 5. While Loop Example.... Facebook Paypal Google Yahoo ==============> 6. Iterable.forEach() Example.... Facebook Paypal Google Yahoo ==============> 7. Stream.forEach() Example.... Facebook Paypal Google Yahoo Process finished with exit code 0