Java - Optional from Stream

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Introduction

Several methods in the Streams API return Optional, OptionalInt, OptionalLong, and OptionalDouble.

For example, the max() method in all stream classes returns an optional object.

The following code shows how to get the maximum integer from IntStream.

Demo

import java.util.Comparator;
import java.util.Optional;
import java.util.OptionalInt;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class Main {
  public static void main(String[] args) {
    // Get the maximum of odd integers from the stream
    OptionalInt maxOdd = IntStream.of(10, 20, 30).filter(n -> n % 2 == 1).max();

    if (maxOdd.isPresent()) {
      int value = maxOdd.getAsInt();
      System.out.println("Maximum odd integer is " + value);
    } else {//from w w  w  . j  av  a2 s  .  c  o  m
      System.out.println("Stream is empty.");
    }

    // Get the maximum of odd integers from the stream
    OptionalInt numbers = IntStream.of(1, 10, 37, 20, 31).filter(n -> n % 2 == 1).max();
    if (numbers.isPresent()) {
      int value = numbers.getAsInt();
      System.out.println("Maximum odd integer is " + value);
    } else {
      System.out.println("Stream is empty.");
    }

    // Get the longest name
    Optional<String> name = Stream.of("Java", "Python", "Li").max(Comparator.comparingInt(String::length));
    if (name.isPresent()) {
      String longestName = name.get();
      System.out.println("Longest name is " + longestName);
    } else {
      System.out.println("Stream is empty.");
    }
  }
}

Result

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