Stream.max() method in Java with Examples

Last Updated : 06 Dec, 2018

Stream.max() returns the maximum element of the stream based on the provided Comparator. A Comparator is a comparison function, which imposes a total ordering on some collection of objects. max() is a terminal operation which combines stream elements and returns a summary result. So, max() is a special case of reduction. The method returns Optional instance.

Syntax :

Optional<T> max(Comparator<? super T> comparator)

Where, Optional is a container object which
may or may not contain a non-null value 
and T is the type of objects
that may be compared by this comparator

Exception : This method throws NullPointerException if the maximum element is null.

Example 1 :

// Implementation of Stream.max() 
// to get the maximum element 
// of the Stream according to the 
// provided Comparator. 
import java.util.*; 
import java.util.Optional; 
import java.util.Comparator; 
  
class GFG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
  
        // Creating a list of integers 
        List<Integer> list = Arrays.asList(-9, -18, 0, 25, 4); 
  
        System.out.print("The maximum value is : "); 
  
        // Using stream.max() to get maximum 
        // element according to provided Comparator 
        // and storing in variable var 
        Integer var = list.stream().max(Integer::compare).get(); 
  
        System.out.print(var); 
    } 
} 

Output :

The maximum value is : 25

Example 2 :

// Implementation of Stream.max() 
// to get the maximum element 
// of the Stream according to the 
// provided Comparator. 
import java.util.*; 
import java.util.Optional; 
import java.util.Comparator; 
  
class GFG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
  
        // Creating a list of integers 
        List<Integer> list = Arrays.asList(-9, -18, 0, 25, 4); 
  
        // Using stream.max() to get maximum 
        // element according to provided Comparator 
        // Here, the smallest element in list 
        // will be stored in variable var 
        Optional<Integer> var = list.stream() 
                     .max(Comparator.reverseOrder()); 
  
        // If a value is present, isPresent() 
        // will return true, else display message 
        if (var.isPresent()) { 
            System.out.println(var.get()); 
        } 
        else { 
            System.out.println("-1"); 
        } 
    } 
} 

Output :

-18

Example 3 :

// Implementation of Stream.max() 
// to get the maximum element 
// of the Stream according to the 
// provided Comparator. 
import java.util.*; 
import java.util.Optional; 
import java.util.Comparator; 
  
class GFG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
  
        // Creating a list of Strings 
        List<String> list = Arrays.asList("G", "E", "E", "K", 
                                          "g", "e", "e", "k"); 
  
        // using Stream.max() method with Comparator 
        // Here, the character with maximum ASCII value 
        // is stored in variable MAX 
        String MAX = list.stream().max(Comparator. 
                       comparing(String::valueOf)).get(); 
  
        // Displaying the maximum element in 
        // the stream according to provided Comparator 
        System.out.println("Maximum element in the "
                           + "stream is : " + MAX); 
    } 
} 

Output :

Maximum element in the stream is : k

Example 4 :

// Implementation of Stream.max() 
// to get the maximum element 
// of the Stream according to the 
// provided Comparator. 
import java.util.*; 
import java.util.Optional; 
import java.util.Comparator; 
  
class GFG { 
  
    // Driver code 
    public static void main(String[] args) 
    { 
  
        // creating an array of strings 
        String[] array = { "Geeks", "for", "GeeksforGeeks", 
                           "GeeksQuiz" }; 
  
        // Here, the Comparator compares the strings 
        // based on their last characters and returns 
        // the maximum value accordingly 
        // The result is stored in variable MAX 
        Optional<String> MAX = Arrays.stream(array).max((str1, str2) ->   
                       Character.compare(str1.charAt(str1.length() - 1),  
                                       str2.charAt(str2.length() - 1))); 
  
        // If a value is present, 
        // isPresent() will return true 
        if (MAX.isPresent())  
            System.out.println(MAX.get());         
        else 
            System.out.println("-1");         
    } 
} 