Java Problem: Returning a string entered as reverse text

Hi,

I'm trying to make a method that returns a string of words in opposite order.

IE/ "The rain in Spain falls mostly on the" would return: "the on mostly falls Spain in rain The"

for this i am not supposed to use any built in Java classes just basic java

So far i have:

    lastSpace = stringIn.length(); 

    for (int i = stringIn.length() - 1; i >= 0; i--){
        chIn = stringIn.charAt(i);
        if (chIn == ' '){
            word = stringIn.substring(i + 1, lastSpace);
            stringOut.concat(word);
            lastS = i;
        }
    }
    word = stringIn.substring(0,lastSpace);
    stringOut.concat(word);

    return stringOut;

My problem is when stringOut is returned to its caller it always is a blank string.

Am i doing something wrong? Maybe my use of string.concat()?

Any help would be much appreciated. Thank you

From stackoverflow

• In Java, Strings are immutable, i.e. they can't be changed. concat() returns a new string with the concatenation. So you want something like this:

  stringOut = stringOut.concat(word);
  

  or

  stringOut += word
  

  as Ray notes, there are more succinct ways to do this though.

• That's because you need to assign the return of concat to something:

  stringOut=stringOut.concat(word)
  

  Strings in Java (and .net) are immutable.

• You would do better if you use the indexOf method of String class, rather than that loop to find each space.

• I felt like coding , so here you go :

  
  import java.util.*;
  
  class ReverseBuffer {
      private StringBuilder soFar;
      public ReverseBuffer() {
          soFar = new StringBuilder();
      }
  
      public void add(char ch) {
          soFar.append(ch);
      }
  
      public String getReversedString() {
          String str = soFar.toString();
          soFar.setLength(0);
          return str;
      }
  }
  
  public class Reverso {
      public static String[] getReversedWords(String sentence) {
          ArrayList < String > strings = new ArrayList < String >();
          ReverseBuffer rb = new ReverseBuffer();
          for(int i = 0;i < sentence.length();i++) {
              char current = sentence.charAt(i);
              if(current == ' ') {
                  strings.add(rb.getReversedString());
              }
              else {
                  rb.add(current);
              }
          }
          strings.add(rb.getReversedString());
          Collections.reverse(strings);
          return (String[])strings.toArray(new String[0]);
      }
  
      public static void main(String[] args) {
          String cSentence = "The rain in Spain falls mostly on the";
          String words[] = Reverso.getReversedWords(cSentence);
          for(String word : words) {
              System.out.println(word);
          }
      }
  }
  

  EDIT: had to call getReversedString once more after the loop.

  Hope this helps !

• 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;
  }
  

  Only API used is String (which should be allowed when manipulating Strings...)