Java 8 Lambda Expressions not working

Question

I'm trying out the following code and compiling it using JDK 1.8.0_66. My code seems to be syntactically correct, did I miss something?

interface Executable {
    void execute();
}

class Runner {
    public void run(Executable e) {
        System.out.println("Executing code block!");
        e.execute();
    }
}

public class HelloWorld {
    public static void main(String[] args) {
        Runner runner = new Runner();

        runner.run(new Executable() {
            public void execute() {
                System.out.println("IN ANONYMOUS CLASS EXECUTE");
            }
        });
    }

    runner.run(() -> System.out.println());

}

throws the following compile error:

App.java:25: error: <identifier> expected
        runner.run(() -> System.out.println());
                  ^
App.java:25: error: illegal start of type
        runner.run(() -> System.out.println());
                   ^
App.java:25: error: ';' expected
        runner.run(() -> System.out.println());

If you're getting compile errors your code is, almost by definition, NOT syntactically correct. — Jim Garrison
– Jim Garrison, Commented Feb 1, 2016 at 7:59
Thanks I feel stupid! Didn't really notice that my lambda expression was outside the Main code block — alcaideredb
– alcaideredb, Commented Feb 1, 2016 at 8:00

Konstantin Yovkov · Accepted Answer · 2016-02-01 07:57:20Z

4

Your statement is outside the block, where the runnner variable is defined. Should be something like:

public static void main(String[] args) {
    Runner runner = new Runner();

    runner.run(new Executable() {
        public void execute() {
            System.out.println("IN ANONYMOUS CLASS EXECUTE");
        }
    });

    runner.run(() -> System.out.println());
}

answered Feb 1, 2016 at 7:57

Konstantin Yovkov

63k8 gold badges107 silver badges152 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Mohammed Aouf Zouag · Accepted Answer · 2016-02-01 07:57:13Z

3

That line of code needs to be inside a code block. So you need to move it into the body of the main method:

Change

} // end of main

runner.run(() -> System.out.println());

to

    runner.run(() -> System.out.println());
} // end of main

answered Feb 1, 2016 at 7:57

Mohammed Aouf Zouag

17.2k4 gold badges44 silver badges68 bronze badges

1 Comment

alcaideredb Over a year ago

Thanks! I didn't notice that! :)

kavita · Accepted Answer · 2017-01-23 17:07:19Z

0

runner.run(() -> System.out.println()); -- is outside main method. Put the code inside the main method and it will work perfectly fine.

answered Jan 23, 2017 at 17:07

kavita

1399 bronze badges

2 Comments

jhhoff02 Over a year ago

This answer is already expressed and realized in the main post's comments

kavita Over a year ago

Thanks. But i didn't notice that. Rating down is not good attitude.

Collectives™ on Stack Overflow

Java 8 Lambda Expressions not working

3 Answers 3

Comments

1 Comment

2 Comments

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

1 Comment

2 Comments

Related