This topic is about Java 11 – Var in Lambda.
Java 11 allows to use var in a lambda expression and it can be used to apply modifiers to local variables.
(@NonNull var value1, @Nullable var value2) -> value1 + value2
Consider the following example −
ApiTester.java
import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; @interface NonNull {} public class APITester { public static void main(String[] args) { List<String> tutorialsList = Arrays.asList("Java", "HTML"); String tutorials = tutorialsList.stream() .map((@NonNull var tutorial) -> tutorial.toUpperCase()) .collect(Collectors.joining(", ")); System.out.println(tutorials); } }
Output
Java HTML
Limitations
There are certain limitations on using var in lambda expressions.
- var parameters cannot be mixed with other parameters. Following will throw compilation error.
(var v1, v2) -> v1 + v2
- var parameters cannot be mixed with other typed parameters. Following will throw compilation error.
(var v1, String v2) -> v1 + v2
- var parameters can only be used with parenthesis. Following will throw compilation error.
var v1 -> v1.toLowerCase()
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