Java Reverse a sentence but not punctuation

Question

Input: My name is Bob.

Output: Bob is name My.

I have seen plenty of examples on how to reverse each word and then word sequence in a sentence. However, I do not think I have seen one that I want-example above. This forum was not helpful, because it only focuses on double quote on start and end of a sentence: How to reverse words in a string but keep punctuation in the right place?

What I tried

public void rev2(String str) {
    String[] arrStr = str.split(" ");
    for (int i = arrStr.length - 1; i >= 0; i--) {
        if (!arrStr[i].contains(".")) {
            System.out.print(arrStr[i] + " ");
        }
    }
}

public static void main(String[] args) {
    Test t = new Test();
    t.rev2("My name is Bob.");
}

The code above does not work as expected. I probably can convert each string to char and use Character.isAlphabet() or may be use pattern?

I could use some ideas. Thanks in advance for your time and help.

Answer 1

Here is a solution that works within the constraints of the question (some of which are assumed):

public void rev2(String str) {
    String[] arrStr = str.split(" ");
    for (int i = arrStr.length - 1; i >= 0; i--) {
        boolean punct = i <= 0 || arrStr[i - 1].contains(".");
        if (!arrStr[i].contains(".")) {
            System.out.print(arrStr[i]);
        } else {
            System.out.print(arrStr[i].substring(0, arrStr[i].length() - 1));
        }
        System.out.print((punct ? ". " : " "));
    }
}

public static void main(String[] args) {
    Tester t = new Tester();
    t.rev2("My name is Bob. I am happy.");
}

Explanation:

The boolean punct looks ahead to see if the next element contains a ".". If so, we are on a sentence boundry and so added a. after the current word. If not, we just put a space. We also add a "." if we are on the last element in the array.

Output: happy am I. Bob is name My.

Answer 2

If all you want to do regarding punctuation is keep the period at the end of the sentence, you can print the words followed by a space or by the period depending on whether they are the first word or not, and you can remove the period from the last word by calling substring() . Something like this:

public class Test {
    public void rev2(String str) {
        String[] arrStr = str.split(" ");
        for (int i = arrStr.length - 1; i >= 0; i--) {
            if (!arrStr[i].contains(".")) {
                System.out.print(arrStr[i] + (i == 0 ? "." : " "));
            } else {
                System.out.print(arrStr[i].substring(0, arrStr[i].length() - 1) + " ");
            }
        }
    }

    public static void main(String[] args) {
        Test t = new Test();
        t.rev2("My name is Bob.");
    }
}

Output: Bob is name My.

Answer 3

If you want a less verbose code:

var list = Arrays.asList("My name is Bob".split(" "));
Collections.reverse(list);
list.stream().map(str -> str.concat(" ")).forEach(System.out::print);