java_upgrade/src/main/java/OptionalDemo.java at main · alcmontejo/java_upgrade · GitHub

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import java.util.Arrays;

import java.util.List;

import java.util.Optional;

import java.util.stream.Stream;

public class OptionalDemo {

public static void main(String[] args) {

Optional<Integer> first = Stream.of(3, 1, 4, 1, 5, 9)

.filter(n -> n > 10)

.findFirst();

System.out.println(first);

// System.out.println(first.isPresent() ? (int) first.get() : 0);

int defaultValue = 0;

System.out.println(first.orElse(defaultValue));

System.out.println(first.orElseGet(() -> defaultValue));

first.ifPresent(System.out::println);

List<String> strings = Arrays.asList("this", "is", "a", "list", "of", "strings");

Optional<String> s = strings.stream()

.findFirst();

System.out.println(s.orElse("No string found; legal values are: " + strings));

System.out.println(s.orElseGet(() -> "No string found; legal values are: " + strings));

System.out.println(s.orElseThrow(IllegalArgumentException::new)); // default constructor

System.out.println(s.orElseThrow(() -> new IllegalArgumentException("Not available")));

s.ifPresent(System.out::println);

}

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