Stream min() method in Java with Examples

25 Jul, 2019
Stream.min() returns the minimum 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. min() is a terminal operation which combines stream elements and returns a summary result. So, min() is a special case of reduction. The method returns Optional instance.
Syntax :
Optional<T> min(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 minimum element is null.
Example 1 : Minimum from list of Integers.
// Java code for Stream.min() method to get// the minimum element of the Stream// according to the provided Comparator.import java.util.*;  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.min() to get minimum        // element according to provided Integer Comparator        Integer var = list.stream().min(Integer::compare).get();          System.out.print(var);    }}
Output :
-18

Example 2 : Reverse comparator to get maximum value using min() function.
// Java code for Stream.min() method// to get the minimum element of the // Stream according to provided comparator.import java.util.*;  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.min() with reverse        // comparator to get maximum element.        Optional<Integer> var = list.stream()                    .min(Comparator.reverseOrder());          // IF var is empty, then output will be Optional.empty        // else value in var is printed.        if(var.isPresent()){        System.out.println(var.get());        }        else{            System.out.println("NULL");        }              }}
Output :
25

Example 3 : Comparing strings based on last characters.
// Java code for Stream.min() method// to get the minimum element of the // Stream according to provided comparator.import java.util.*;  class GFG {      // Driver code    public static void main(String[] args)    {          // creating an array of strings        String[] array = { "Geeks", "for", "GeeksforGeeks",                           "GeeksQuiz" };          // The Comparator compares the strings        // based on their last characters and returns        // the minimum value accordingly.        Optional<String> MIN = Arrays.stream(array).min((str1, str2) ->                     Character.compare(str1.charAt(str1.length() - 1),                                       str2.charAt(str2.length() - 1)));          // If a value is present,        // isPresent() will return true        if (MIN.isPresent())             System.out.println(MIN.get());         else            System.out.println("-1");     }}
Output :
for

Akanksha_Rai
Java - util package
Java-Functions
java-stream
Java-Stream interface
Java
Java
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