Lambda function in Java 8 with no parameter and returning value

Question

I want to convert a simple Java function to a lambda 8 function without any parameter, and then call it:

public int getMissing() {
  return 0;
}

how to convert above to java8 lambda format?

Answer 1

Your case is similar with Supplier in Java 8

 Supplier<Integer> supplier = () -> 0;
 System.out.println(supplier.get());

Answer 2

You do not really convert methods into lambdas directly. Lambdas are more-or-less implementations of Functional Interfaces created on the fly without the overhead of the classic anonymous inner function approach.

So, if you want to pass it around as a lambda, you need to find a matching Functional Interface and assign a lambda to it.

In this case, you have a method without parameters that returns an int and one of the possible choices would be to use IntSupplier:

IntSupplier supplier = () -> 0;

and now, you can call it by doing:

supplier.getAsInt()

---

If you want to return a boxed Integer, you would need to use a generic Supplier<T>:

Supplier<Integer> supplier = () -> 0;
supplier.get(); // 0

Answer 3

It isn't clear what you intend to do with that value, but a generator has the form () -> Int - something like,

IntStream.generate(() -> 0).limit(1).forEach(System.out::println);

If you omit the limit(1) then you will get an infinite number of zeros, if you need to preserve order use forEachOrdered (instead of forEach).