Main.java Source code

Introduction

Here is the source code for Main.java

Source

import java.util.ArrayList;
import java.util.List;
import java.util.Optional;

public class Main {
    public static void main(String[] args) {

        Optional<String> value = Optional.of("some value");
        System.out.println(value.isPresent());
        System.out.println(value.get());
        String str = null;
        // Optional.of(str);

        Optional<Integer> o = Optional.empty();
        System.out.println(o.isPresent());
        System.out.println(o.orElse(42));

        List<Integer> results = new ArrayList<>();
        Optional<Integer> second = Optional.of(3);
        second.ifPresent(results::add); // must operate via side-effects,
                                        // unfortunately...
        System.out.println(results);

        o = Optional.empty();
        System.out.println(o.orElse(42));

        o = Optional.of(42);
        System.out.println(o.get());

        o = Optional.empty();
        o.get();
    }

}