In this post, we will write a Java program to reverse each word of an input String.

The logic is very simple. just follow the below steps:

1. Split the input String using the split() method, the split method returns a string array.
2. Iterate over string array and which internally makes a call to reverseWithStringConcat() method
3. The reverseWithStringConcat() method is responsible to reverse each word and return the same
4. Concatenated each reverse word using the + operator (in this program we are using only String, not StringBuilder or StringBuffer)
5. Call display() method to print original and reverse strings

Java Program To Reverse Each Word Of A String

/**
 * Java Program To Reverse Each Word Of A String.
 * 
 * @author javaguides.net
 *
 */
public class ReverseEachWord {
    public static void main(String[] args) {

        reverseEachWord("java guides");

        reverseEachWord("I am string not reversed");

        reverseEachWord("Reverse Me");

    }

    private static String reverseEachWord(String originalStr) {

        // split the sentence by words using split method
        String[] words = originalStr.split(" ");

        String reverseStr = "";

        // Iterate over String array
        for (String word: words) {
            // reverse each word by calling reverseWithStringConcat method
            reverseStr = reverseStr + reverseWithStringConcat(word) + " ";
        }

        display(originalStr, reverseStr);
        return reverseStr;
    }

    private static final void display(String original, String reverse) {
        System.out.println(original);
        System.out.println(reverse);
        System.out.println("----------------------------");
    }
    private static final String reverseWithStringConcat(String string) {
        String reverseWord = "";
        for (int i = (string.length() - 1); i >= 0; i--) {
            reverseWord = reverseWord + string.charAt(i);
        }
        return reverseWord;
    }
}

Output:

java guides
avaj sediug 
----------------------------
I am string not reversed
I ma gnirts ton desrever 
----------------------------
Reverse Me
esreveR eM 
----------------------------

Using StringBuilder

Now, let's use StringBuilder to rewrite the above program ( We suggest you use StringBuilder for concatenation)

public class ReverseEachWord {
    public static void main(String[] args) {

        reverseEachWord("java guides");

        reverseEachWord("I am string not reversed");

        reverseEachWord("Reverse Me");

    }

    private static String reverseEachWord(String originalStr) {

        // split the sentence by words using split method
        String[] words = originalStr.split(" ");

        StringBuilder reverseStr = new StringBuilder();

        // Iterate over String array
        for (String word : words) {
            // reverse each word by calling reverseWithStringConcat method
            StringBuilder temp = new StringBuilder(word);
            reverseStr.append(temp.reverse());
            reverseStr.append(" ");
        }

        display(originalStr, reverseStr.toString());
        return reverseStr.toString();
    }

    private static final void display(String original , String reverse){
        System.out.println(original);
        System.out.println(reverse);
        System.out.println("----------------------------");
    }
}

Output:

java guides
avaj sediug 
----------------------------
I am string not reversed
I ma gnirts ton desrever 
----------------------------
Reverse Me
esreveR eM 
----------------------------

You can optimize the above program logic.

Please write comments if you find anything incorrect, or if you want to share more information about the topic discussed above.

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