Java Stream max() Example

1. Introduction

This tutorial explains how to use the max() method of the Java Stream API. The max() method is used to determine the maximum element of a stream according to a given comparator. This is a common operation when dealing with collections of data that require ordering or comparison.

Key Points

1. The max() method is used to find the maximum element in a stream based on a provided comparator.

2. It returns an Optional type because the stream may be empty.

3. The Java Stream max() method is a terminal operation that returns the largest element in the Stream.

2. Program Steps

1. Create a Stream of integers.

2. Apply the max() method with a comparator to find the largest number.

3. Handle the result wrapped in an Optional.

3. Code Program

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

public class StreamMaxExample {

    public static void main(String[] args) {
        // Stream of integers
        Stream<Integer> numberStream = Stream.of(10, 45, 75, 30, 90);

        // Find max in stream of numbers
        Optional<Integer> maxNumber = numberStream.max(Comparator.naturalOrder());
        maxNumber.ifPresent(max -> System.out.println("The maximum number is: " + max));

        // Stream of strings
        Stream<String> stringStream = Stream.of("Apple", "Orange", "Banana", "Lemon", "Peach");

        // Find max in stream of strings
        Optional<String> longestString = stringStream.max(Comparator.comparingInt(String::length));
        longestString.ifPresent(longest -> System.out.println("The longest string is: " + longest));
    }
}

Output:

The maximum number is: 90
The longest string is: Orange

Explanation:

1. Stream.of(10, 45, 75, 30, 90) creates a stream of integers.

2. numberStream.max(Comparator.naturalOrder()) applies the max() operation with the natural ordering of integers to find the highest value.

3. maxNumber.ifPresent(max -> System.out.println("The maximum number is: " + max)) checks if a maximum value is present and prints it.

4. Stream.of("Apple", "Orange", "Banana", "Lemon", "Peach") creates another stream, this time with strings.

5. stringStream.max(Comparator.comparingInt(String::length)) uses a comparator based on string length to find the longest string in the stream.

6. longestString.ifPresent(longest -> System.out.println("The longest string is: " + longest)) prints the longest string if it exists.