Studying Java 9, I saw a new method that works with collections: List.of , example:
List<String> frutas = List.of("maça", "laranja");
I already used Arrays.asList , for example:
List<String> frutas = Arrays.asList("maça", "laranja");
What's the difference between using these methods?
Arrays.asList ()
Returns a fixed-length list supported by the specified array. This method acts as a bridge between array-based and collection-based APIs.
Example:
package com.exemplo;
import java.util.Arrays;
import java.util.List;
public class ArrayExemplo {
public static void main (String args[]) {
// cria um array de strings
String a[] = new String[]{"abc","def","fhi","jkl"};
List list1 = Arrays.asList(a);
// imprime a lista
System.out.println("A lista é:" + list1);
}
}
List.of
Oracle has introduced some convenient methods for creating List , Set , Map and Map.Entry objects immutable. These utility methods are used to create empty or non-empty collection objects .
In Java SE 8 and earlier, we can use the Collections class's utility methods, such as unmodifiableXXX to create Collection immutable objects . For example, if we want to create an immutable list, we can use the Collections.unmodifiableList method.
However, these Collections.modifiableXXX methods are very tedious and verbose . To overcome these shortcomings, Oracle added some utility methods to the List , Set and Map interfaces.
The List and Set interfaces have " of () " methods to create an empty or non-empty immutable List or Set as shown below :
List umListImutavelVazio = List.of();
List not empty:
List umListImutavel = List.of("um","dois","tres");