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());

• Jim Garrison: If you're getting compile errors your code is, almost by definition, NOT syntactically correct.
• alcaideredb: Thanks I feel stupid! Didn't really notice that my lambda expression was outside the Main code block

Answer 1

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());
}

Answer 2

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

• alcaideredb: Thanks! I didn't notice that! :)

Answer 3

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

• jhhoff02: This answer is already expressed and realized in the main post's comments
• kavita: Thanks. But i didn't notice that. Rating down is not good attitude.