How to reverse words in string in java without using split and stringtokenizer

Question

I want to reverse words in string of java without using split method and StringTokenizer.

For example, How are you must be printed in you are How.

I tried but I failed to do it.

Any help will be appreciated.

possible duplicate of [Reverse String Word by Word in Java](http://stackoverflow.com/questions/9105277/reverse-string-word-by-word-in-java) — Alex K, Nov 10 '13 at 16:56

score 2 · Accepted Answer · answered Nov 10 '13 at 14:43

Try below code snippet

import java.util.ArrayList;
public class ReverseString
{
    public static void main(String args[])
    {
        String myName = "Here we go";
        ArrayList al = new ArrayList();
        al = recursiveReverseMethod(myName,al);
        al.trimToSize();
        StringBuilder sb = new StringBuilder();
        for(int i = al.size()-1; i>=0;i--)
        {
            sb.append(al.get(i)+" ");

        }
        System.out.println(sb);

    }
    public static ArrayList  recursiveReverseMethod(String myName,ArrayList al)
    {

        int index = myName.indexOf(" ");
        al.add(myName.substring(0, index));
        myName  = myName.substring(index+1);
        if(myName.indexOf(" ")==-1)
        {
            al.add(myName.substring(0));
            return al;
        }
        return recursiveReverseMethod(myName,al);

    }
}

score 1 · Answer 2 · edited May 23 '17 at 12:15

Here is another flavor based on the old time logic of String reversal in 'C'., from this thread.,

class testers {
    public static void main(String[] args) {
        String testStr="LongString";
        testers u= new testers();
        u.reverseStr(testStr);
    }
    public void reverseStr(String testStr){
        char[] d= testStr.toCharArray();
        int i;
                int length=d.length;
                int last_pos;
                last_pos=d.length-1;
                for (i=0;i<length/2;i++){
                    char tmp=d[i];
                    d[i]=d[last_pos-i];
                    d[last_pos-i]=tmp;

                }
                System.out.println(d);
              }
    }

score 1 · Answer 3 · answered Nov 10 '13 at 15:26

I would do this:

public static String reverseWordsWithoutSplit(String sentence){
    if (sentence == null || sentence.isEmpty()) return sentence;
    int nextSpaceIndex = 0;
    int wordStartIndex = 0;
    int length = sentence.length();
    StringBuilder reversedSentence = new StringBuilder();
    while (nextSpaceIndex > -1){
        nextSpaceIndex = sentence.indexOf(' ', wordStartIndex);
        if (nextSpaceIndex > -1) reversedSentence.insert(0, sentence.substring(wordStartIndex, nextSpaceIndex)).insert(0, ' ');
        else reversedSentence.insert(0, sentence.subSequence(wordStartIndex, length));
        wordStartIndex = nextSpaceIndex + 1;
    }

    return reversedSentence.toString();
}

alternatively u may also use lastIndexOf() from String class and append() from StringBuilder. — Prateek, Nov 10 '13 at 15:27

How to reverse words in string in java without using split and stringtokenizer

3 Answers3