Java 8 – Find Minimum Value in a List

Introduction

Finding the minimum value in a list is a common task in programming, especially when you need to identify the smallest number in a set of data. Java 8 introduced the Stream API, which makes this operation more straightforward and allows you to write code in a more functional and declarative style. In this guide, we’ll explore how to find the minimum value in a list using Java 8 Streams, covering different types of lists including integers and custom objects.

Table of Contents

• Problem Statement
• Solution Steps
• Java Program
  • Finding Minimum Value in a List of Integers
  • Finding Minimum Value in a List of Custom Objects
• Advanced Considerations
• Conclusion

Problem Statement

The task is to create a Java program that:

• Accepts a list of elements.
• Finds the minimum value in the list.
• Outputs the minimum value.

Example 1:

• Input: List of integers [1, 3, 7, 0, 5]
• Output: 0

Example 2:

• Input: List of custom Student objects, find the student with the minimum age.
• Output: Student with the lowest age.

Solution Steps

1. Input List: Start with a list of elements that can either be hardcoded or provided by the user.
2. Find Minimum Value Using Streams: Use the min() method to find the minimum value in the list.
3. Display the Result: Print the minimum value.

Java Program

Finding Minimum Value in a List of Integers

import java.util.Arrays;
import java.util.List;
import java.util.Optional;

/**
 * Java 8: Find Minimum Value in a List of Integers Using Streams
 * Author: https://www.rameshfadatare.com/
 */
public class FindMinInList {

    public static void main(String[] args) {
        // Step 1: Take input list
        List<Integer> numbers = Arrays.asList(1, 3, 7, 0, 5);

        // Step 2: Find the minimum value in the list using streams
        Optional<Integer> minNumber = numbers.stream()
                                             .min(Integer::compareTo);

        // Step 3: Display the result
        minNumber.ifPresent(min -> System.out.println("Minimum value: " + min));
    }
}

Output

Minimum value: 0

Explanation

• The stream() method is used to create a stream from the list of integers.
• The min() method, combined with Integer::compareTo, finds the minimum value in the stream.
• The result is an Optional<Integer>, which is used to safely print the minimum value.
• The output shows that the minimum value in the list is 0.

Finding Minimum Value in a List of Custom Objects

import java.util.Arrays;
import java.util.List;
import java.util.Optional;

/**
 * Java 8: Find Minimum Value in a List of Custom Objects Using Streams
 * Author: https://www.rameshfadatare.com/
 */
public class FindMinInCustomObjects {

    public static void main(String[] args) {
        // Step 1: Take input list of custom objects
        List<Student> students = Arrays.asList(
                new Student("Raj", 25),
                new Student("Anita", 30),
                new Student("Vikram", 22)
        );

        // Step 2: Find the student with the minimum age using streams
        Optional<Student> youngestStudent = students.stream()
                                                    .min((s1, s2) -> Integer.compare(s1.getAge(), s2.getAge()));

        // Step 3: Display the result
        youngestStudent.ifPresent(student -> 
            System.out.println("Youngest student: " + student.getName() + ", Age: " + student.getAge())
        );
    }
}

// Custom class Student
class Student {
    private String name;
    private int age;

    public Student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }
}

Output

Youngest student: Vikram, Age: 22

Explanation

• The list of Student objects is processed to find the student with the minimum age.
• The min() method is used with a custom comparator (s1, s2) -> Integer.compare(s1.getAge(), s2.getAge()) to determine the student with the lowest age.
• The result is an Optional<Student>, which is used to safely print the details of the youngest student.
• The output shows that "Vikram" is the youngest student with an age of 22.

Advanced Considerations

• Handling Empty Lists: The min() method returns an Optional, which is a safe way to handle cases where the list might be empty. If the list is empty, the Optional will be empty, and you can handle this case appropriately.

• Custom Comparators: If you need to find the minimum based on custom criteria, you can provide a custom comparator to the min() method. This is especially useful when working with complex objects.

• Parallel Streams: For large lists, consider using parallelStream() to leverage multi-core processors for finding the minimum value more efficiently.

Conclusion

This guide provides methods for finding the minimum value in a list using Java 8 Streams, covering both simple lists like integers and more complex lists like custom objects. Java 8 Streams offer a powerful and concise way to perform this operation, making your code more readable and maintainable. Depending on your specific use case, you can easily apply the techniques demonstrated in this guide to achieve the desired result.