Java Collections min()

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In this guide, you will learn about the Collections min() method in Java programming and how to use it with an example.

1. Collections min() Method Overview

Definition:

The min() method of the Collections class in Java is used to return the minimum element of the given collection, according to the natural ordering of its elements.

Syntax:

Collections.min(Collection<? extends T> coll)

Parameters:

coll: The collection whose minimum element is to be determined.

Key Points:

- The collection must not be empty, or else a NoSuchElementException will be thrown.

- All elements in the collection must be mutually comparable using the provided comparator (or the natural ordering if using the method without a comparator), otherwise, a ClassCastException is thrown.

- There is an overloaded version of min() that takes a custom comparator as an argument to determine the minimum element based on the comparator's ordering.

2. Collections min() Method Example

import java.util.*;

public class CollectionsMinExample {
    public static void main(String[] args) {
        List<Integer> numbers = new ArrayList<>(Arrays.asList(15, 23, 7, 31, 12));

        // Finding the minimum number in the list
        int minNumber = Collections.min(numbers);
        System.out.println("Minimum number in the list: " + minNumber);

        // Finding the minimum string based on length using a custom comparator
        List<String> words = new ArrayList<>(Arrays.asList("apple", "banana", "kiwi"));
        String shortestWord = Collections.min(words, Comparator.comparingInt(String::length));
        System.out.println("Shortest word in the list: " + shortestWord);
    }
}

Output:

Minimum number in the list: 7
Shortest word in the list: kiwi

Explanation:

In the provided example, we first create a list of integers and determine the minimum number using the min() method. 

Next, we create a list of strings and determine the shortest word by providing a custom comparator to the min() method that compares strings based on their lengths.