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Find Longest Word in a String in Java

beginner· Strings · String

Problem

The longest word in a sentence is whichever word has the most characters once every word's length has been compared.

Given a sentence, find its longest word.

Input

The quick brown fox jumps

Output

Longest word: quick

Java Program

Java

public class FindLongestWord {
    public static void main(String[] args) {
        String str = "The quick brown fox jumps";
        String[] words = str.split(" ");
        String longest = words[0];

        for (String word : words) {
            if (word.length() > longest.length()) { // update whenever a strictly longer word is found
                longest = word;
            }
        }

        System.out.println("Longest word: " + longest);
    }
}

▶ Run Code

Output

Longest word: quick

Core Logic

Splitting the sentence into words and keeping track of the longest one seen so far, one pass through the array, finds the winner.

How It Works

1str.split(" ") breaks the sentence into an array of individual words.
2longest starts out holding the first word, words[0].
3A loop visits every word, comparing its length against longest.length() with >.
4Whenever a longer word is found, longest is updated to that word.

For "The quick brown fox jumps", 'quick', 'brown', and 'jumps' all tie at 5 letters — longest is updated to 'quick' first and, since later words aren't strictly longer, it stays 'quick'.

💡

Key Point: Using > rather than >= means the first word to reach the maximum length wins any tie, keeping the result deterministic.

Complexity

Time Complexity: O(n)Space Complexity: O(n)

Why: split() allocates an array holding every word, and the scan then makes one pass over it comparing lengths.

Key Concepts

String.split()String.length()running maximum

Approach 2: Java 8

Java

import java.util.Arrays;
import java.util.Comparator;

public class FindLongestWordStream {
    public static void main(String[] args) {
        String str = "The quick brown fox jumps";
        // Compares every word by length and keeps the longest one
        String longest = Arrays.stream(str.split(" "))
            .max(Comparator.comparingInt(String::length))
            .orElseThrow();
        System.out.println("Longest word: " + longest);
    }
}

▶ Run Code

Output

Longest word: quick

Core Logic

Once the words are split, a stream can find the longest one directly instead of a manual running-maximum loop.

How It Works

1Arrays.stream(str.split(" ")) turns the split words into a Stream<String>.
2Comparator.comparingInt(String::length) builds a comparator that compares two words purely by their length.
3.max(...) compares every word using that comparator and keeps the single longest one, wrapped in an Optional.
4.orElseThrow() unwraps the result, since the sentence is known not to be empty here.

Comparing every word in "The quick brown fox jumps" by length picks out 'quick' as the longest, matching the manual version's first-seen tiebreak.

💡

Key Point: Comparator.comparingInt() avoids writing a custom Comparator by hand — it builds one directly from a method that extracts an int key from each element.

Complexity

Time Complexity: O(n)Space Complexity: O(n)

Why: split() still allocates an array holding every word, and max() then makes one pass over it comparing lengths.

Key Concepts

StreamComparator.comparingInt()max()

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