Count Words in Java: Solution, Explanation & Practice

Count words in a sentence

Problem summary

Write a program that counts the number of words in a sentence.

Starter code

public class Main {
    public static void main(String[] args) {
        String sentence = "Java is a programming language"; // Test case 1
        
        // Count words
        // Print: Word count: <result>
    }
}

Expected output and test cases

5 words in sentence
```
Word count: 5
```
Single word
```
Word count: 1
```
Three words
```
Word count: 3
```

Hints

Split by space: .split(" ")
Count array length after split
Handle multiple spaces with .split("\\s+")

Validated solution

Reveal Java solution

public class Main {
    static int wordCount(String text) {
        String trimmed = text.trim();
        return trimmed.isEmpty() ? 0 : trimmed.split("\\s+").length;
    }
    public static void main(String[] args) {
        System.out.println("Word count: " + wordCount("Java programs can be readable"));
    }
}

How to approach the problem

Trim first so leading and trailing whitespace cannot create a fake word. Splitting the remaining text on one-or-more whitespace characters treats repeated spaces, tabs, and newlines as one separator.

Approach

Trim the input.
Return zero if nothing remains.
Split on the whitespace run pattern.

Time and space complexity

Time: O(n). Space: O(n).

Edge cases to test

Whitespace-only input has zero words.
A word definition involving punctuation or apostrophes needs a more specific tokenizer.

Common mistakes

Calling split on an empty trimmed string and treating the result as one word.
Splitting only on a literal single space.

Follow-up challenge

Count words while preserving quoted phrases as one token.

Related Strings exercises

Practice all Strings exercises · Run this idea in the Java compiler