Variable Capture and Effectively final

• Local variables

• Instance variables

• Static variables

Local Variable Capture

public interface MyFactory {
    public String create(char[] chars);
}

String myString = "Test";

MyFactory myFactory = (chars) -> 
			String.join(":",myString, new String(chars));

1. 지역변수는 final 로 선언돼있어야한다.

2. final 로 선언되지 않은 지역변수는 final 처럼 동작해야한다.즉, 값의 재할당이 일어나면 안 된다.

Any local variable, formal parameter, or exception parameter used but not declared in a lambda expression must either be declared final or be effectively final

Instance Variable Capture

public class EventConsumerImpl {

    private String name = "MyConsumer";

    public void attach(MyEventProducer eventProducer){
        eventProducer.listen(e -> {
            System.out.println(this.name);
        });
    }
}

Static Variable Capture

public class EventConsumerImpl {
    private static String someStaticVar = "Some text";

    public void attach(MyEventProducer eventProducer){
        eventProducer.listen(e -> {
            System.out.println(someStaticVar);
        });
    }
}