Reverse the words in a given string sentence

In this post, you will learn how to reverse the words in a given string sentence using Java. To reverse the words in a given String sentence in Java, you can split the sentence into words, reverse their order, and then join them back into a new sentence.

Here’s how you can achieve this:

package com.javacodepoint.string;

public class ReverseWordsInSentence {
	
	public static String reverseSentence(String input) {
		if (input == null || input.isEmpty()) {
			return input; // If the input is null or empty, return as it is.
		}

		// Split the input sentence into words
		String[] words = input.trim().split("\\s+");

		// Reverse the order of words
		StringBuilder reversedSentence = new StringBuilder();
		for (int i = words.length - 1; i >= 0; i--) {
			reversedSentence.append(words[i]);
			if (i > 0) {
				reversedSentence.append(" "); // Add space between words
			}
		}

		return reversedSentence.toString();
	}

	public static void main(String[] args) {
		String sentence = "This is a sample string sentence";
		String reversedSentence = reverseSentence(sentence);

		System.out.println("Input Sentence: " + sentence);
		System.out.println("Reversed Sentence: " + reversedSentence);
	}
}

OUTPUT:

Input Sentence: This is a sample string sentence.
Reversed Sentence: sentence. string sample a is This

Explanation:

In this program, we first split the input sentence into words using the split method with the regular expression "\\s+", which matches one or more whitespace characters (spaces, tabs, or newlines). The resulting words array contains individual words.

Next, we create a StringBuilder named reversedSentence to build the reversed sentence. We iterate through the words array in reverse order, appending each word to the reversedSentence. We also add a space between words (except before the first word) to separate them properly.

Finally, we return the reversedSentence as the reversed sentence.

Learn also: Reverse a string without using the reverse() method.