Table of Contents
- Initialize List of Strings with values
- Arrayss asList
- Stream.of [Java 8]
- List.of [Java 9]
- Using ArrayLists add method
- Using guava library
In this post, we will see how to initialize List of String in java.
Can you initialize List of String as below:
1 2 3 | List list = new List[]; |
You can't because List is an interface and it can not be instantiated with new List[].
You need to instantiate it with the class that implements the List interface.
Here are the common java Collections classes which implement List interface.
1 2 3 4 5 6 7 8 9 10 11 12 13 | // ArrayList List list1 = new ArrayList[]; // LinkedList List list2 = new LinkedList[]; // Vector List list3 = new Vector[]; // CopyOnWriteArrayList List list4 = new CopyOnWriteArrayList[]; |
In most of the cases, you will initialize List with ArrayList as below.
1 2 3 4 | // ArrayList List list1 = new ArrayList[]; |
If you are using java 7 or greaterthan you can use diamond operator with generics.
1 2 3 4 | // ArrayList List list1 = new ArrayList[]; |
Initialize List of Strings with values
There are many ways to initialize list of Strings with values.
Arrayss asList
You can use Arrayss asList method to initialize list with values.
1 2 3 | List list1 = Arrays.asList["India","China","Bhutan"]; |
Stream.of [Java 8]
You can use java 8s Stream to initialize list of String with values.
1 2 3 | List list1 = Stream.of["India","China","Bhutan"].collect[Collectors.toList[]]; |
List.of [Java 9]
Finally, java has introduced a of[] method in List class to initialize list with values in java 9.
1 2 3 | List list1 = List.of["India","China","Bhutan"]; |
Using ArrayLists add method
You can obviously initialize ArrayList with new operator and then use add method to add element to the list.
1 2 3 4 5 6 7 | // ArrayList List list1 = new ArrayList[]; list1.add["India"]; list1.add["China"]; list1.add["Bhutan"]; |
Using guava library
You can use guava library as well.
1 2 3 | List list1 = Lists.newArrayList["India","China","Bhutan"]; |
Here is the complete example.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 | package org.arpit.java2blog; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; import java.util.stream.Stream; public class ListOfStringsMain { public static void main[String[] args] { List list1 = new ArrayList[]; list1.add["India"]; list1.add["China"]; list1.add["Bhutan"]; System.out.println[list1]; // Using Arrays.asList List list2= Arrays.asList["India","China","Bhutan"]; System.out.println[list2]; // Using Stream.of List list3 = Stream.of["India","China","Bhutan"].collect[Collectors.toList[]]; System.out.println[list3]; List list4 = List.of["India","China","Bhutan"]; System.out.println[list4]; } } |
Output:
Thats all about how to initialize List of String in java.