Reverse a given sentence in Java

Question

Can anyone tell me how to write a Java program to reverse a given sentence?

For example, if the input is:

\"This is an interview question\"

Answer 1

String[] words = sentence.split(" ");
String[] reversedWords = ArrayUtils.reverse(words);
String reversedSentence = StringUtils.join(reversedWords, " ");

(using ArrayUtils and StringUtils from commons-lang, but these are easy methods to write - just a few loops)

Answer 2

Shortest Answer

public class ReverseSentance {

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    System.out.println("Enter a sentance");
    String inputString = sc.nextLine();

    String[] words = inputString.split(" ");

    List<String> reverseWord = Arrays.asList(words);
    Collections.reverse(reverseWord);

    Iterator itr = reverseWord.iterator();

    while (itr.hasNext()) {
        System.out.print(itr.next() + " ");
    }
}

}

OR

public class ReverseSentance {

public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    System.out.println("Enter a sentance");
    String inputString = sc.nextLine();

    String[] words = inputString.split(" ");

    for (int i = words.length-1 ; i >= 0; i--) {
        System.out.print(words[i] +" ");
    }
}

Answer 3

nicer approach probably.. had seen the logic somewhere..here is my code which might do the job.

    public class revWords {

    public static void main(String[] args) {

        revWords obj = new revWords();
        String print = obj.reverseWords("I am God");
        System.out.println(print);

    }

    public String reverseWords(String words)
    {
      if(words == null || words.isEmpty() || !words.contains(" "))
        return words;

      String reversed = "";
      for( String word : words.split(" "))
        reversed = word + " " + reversed;

      return reversed;
    }

}

Answer 4

I don't think you should use any library.. 1) Reverse whole string 2) Reverse each word.

public static void revWord(char[] a) {

    // reverse whole
    revWord(a, 0, a.length);

    int st = -1;
    int end = -1;

    for (int i = 0; i < a.length; i++) {

        if (st == -1 && a[i] != ' ') {
            st = i;
        }
        if (end == -1 && a[i] == ' ' ) {
            end = i;
        }
        if(i == a.length-1){
            end=i+1;
        }

        if (st != -1 && end != -1) {
            revWord(a, st, end );

            st = -1;
            end = -1;
        }

    }

}

public static void revWord(char[] a, int s, int l) {
    int mid = (l - s) / 2;
    l--;

    for (int i = 0; i < mid; i++, l--) {
        char t = a[s+i];
        a[s+i] = a[l];
        a[l] = t;
    }
}

`

Answer 5

a every boring bit of java:

List<String> l = new ArrayList<String>(Arrays.asList("this is an interview question".split("\\s")));
Collections.reverse(l);
StringBuffer b = new StringBuffer();
for( String s : l ){
    b.append(s).append(' ');
}
b.toString().trim();

in groovy it's a little bit more readable:

"this is an interview question"
    .split("\\s")
    .reverse()
    .join(' ')

Answer 6

Just being different: a recursive solution. Doesn't add any extra spaces.

public static String reverse(String s) {
   int k = s.indexOf(" ");
   return k == -1 ? s : reverse(s.substring(k + 1)) + " " + s.substring(0, k);
}


System.out.println("[" + reverse("This is interview question") + "]");
// prints "[question interview is This]"

---

I will also improve on the split solution by using \b instead (it's so obvious!).

    String[] parts = "Word boundary is better than space".split("\\b");
    StringBuilder sb = new StringBuilder();
    for (int i = parts.length; i --> 0 ;) {
        sb.append(parts[i]);
    }
    System.out.println("[" + sb.toString() + "]");
    // prints "[space than better is boundary Word]"