Infinite loop problem

Question

Hi there,
This is the second time I have posted this problem, as the last solution I was offered did not seem to work. Here is the problem:
I have written a method to search through a text file for a word and replace it with another word. That word can either be on its own in the document or as part of another word. So, if the search word was "foot" and the replace word was "dog", the word "football" in the document would become "dogball".
This method works fine, except for when the replace word is the same as the search word. Basically, if someone searched for "dog" and wanted to replace it with "dog dog" or even just "dog", the program goes into an infinite loop. I understand why it is doing this, but I don't know how to prevent it from happening.
Now, to make it worse I have to stick to this array style structure and method of solving the problem. I know there is a way to do this by building temporary strings and then concatenating them at the end and returning them to their previous position in the array. The reason I know this is because a friend of mine has managed it. She also happens to be a girl.
So, I am asking you all to assist in defending men's intelligence by helping me see where I am going wrong in this method. Please.
Here is the method:
// Search the document for a string and replace it with another string        
     public String [] SearchReplace() {
          // Declare variables to be used in the method
          String SecondSubstring;
          String FirstSubstring;
          int ReplaceNumber = 0;
          // Loop through the lines of text stored as strings contained in the array
          for (int i = 0; i < NumberOfLines; i++) {
                    // As long as the string contains an instance of the search string, run the method                    
                    while (StrArray.indexOf(SearchW) >= 0) {
                         // Make a string of all the characters after the search word
                         SecondSubstring = StrArray[i].substring(StrArray[i].indexOf(SearchW) + SearchW.length());
                         // Make a string of all the characters before the search word
                         FirstSubstring = StrArray[i].substring(0, StrArray[i].indexOf(SearchW));
                         // Concatenate FirstSubstring with the replace word to make a new string
                         String FirstHalf = FirstSubstring.concat(ReplaceW);
                         // Concatenate the new string with SecondSubstring to make the whole replaced string
                         String FullString = FirstHalf.concat(SecondSubstring);
                         // Put this altered string back to its original place in the array
                         StrArray[i] = FullString;
                         // Increment ReplaceNumber to count the replacements made
                         ReplaceNumber++;
          // Print the numbers of replacements made
          System.out.println("\nA total of " + ReplaceNumber + " changes made.\n");
          // Display the searched and replaced contents of the file
          return StrArray;
Any suggestions, pointers or solutions would be much appreciated.
Thanks very much.

Answer 1

Doing it the "old fashioned" way:
You need to keep track of a "from index" so you don't search through parts of the string you've already replaced:
       public static void main(String args[]) {          
          try {     
               String[] lines = new String[] {
                    "the dog went up the dog hill",
                    "all dogs go to dog heaven",
                    "the dogball takes place on 3rd april"
               lines = replace(lines, "dog", "dog dog");
               for (int i = 0; i < lines.length; i++) {
                    System.out.println(lines);
          } catch (Exception e) {
               e.printStackTrace();
     private static String[] replace(String[] lines, String searchWord, String replaceWord) {
          if (searchWord.equals(replaceWord)) return lines; // nothing to do          
          for (int i = 0; i < lines.length; i++) {
               int fromIndex = 0; // from index to do indexOf
               String line = lines[i];
               while (line.indexOf(searchWord, fromIndex) != -1) {
                    final int index = line.indexOf(searchWord, fromIndex);
                    line = line.substring(0, index) + replaceWord + line.substring(index + searchWord.length());
                    fromIndex = (line.substring(0, index) + replaceWord).length();
               lines[i] = line; // replace
          return lines;