java - How to find a specific occurrence of a string inside of a string -

the problem this, i'm trying find , 1 occurrence of string, when way can 1 using keyword occurs multiple times.

ex. 4 potato, 4 (string want), 4 house, 4 car

how string want, when can't type in keywords string might contain.

imagine trying take 1 paragraph out of essay.

i've tried stringy.replaceall(str1, str2); variable, no avail. happens replace of string (go figure name replace all)

package com.donovan.cunningham;  import java.util.arraylist; import java.util.random;  public class essaycreator { //creating varz     private static string[] lf = {"happy", "sad", "unhappy", "atractive",         "fast", "lazy"};     private static string[] op = {"estatic", "melhencohly", "depressed",          "alluring", "swift", "lackadaisical"};     private static string pf = "   ";     private static string temp[];     private static string conv = "   ";     private static string comm = ", ";     private static random random = new random();     private arraylist<string> array = new arraylist<string>();      public static void converter(string in) {         in = in.replace(comm, conv);         (int = 0; < lf.length; i++){                 in = in.replace(lf[i], op[i]);         }         in = in.replace(conv, comm);         //int rand = random.nextint(in.indexof(pf));         (int = 0; < in.indexof(pf); i++){             /*                 want exact string of essay                 i'd convert pf conv, , remove paragraph                  change order             } */         }          creategui.output.settext(in);         sound.stopsound();     } } 

thanks

your question not clear though. want (1) find occurrence string don't know or want (2) replace occurrence string know?

the naive way (1) chop text space , put them in string-to-integer hashmap calculate occurrence string. can scan hashmap find n-occurence strings

for (2), supposed know key string want find, can apply indexof(string str, int fromindex) in string recursively followed:

int occurencecount = 0; string input = "here text key_word1, key_word2, ...etc";  stringbuffer output = new stringbuffer(); int index = input.indexof("key_word"); int copiedindex = 0;  for(index>0) {   output.append(input.substring(copiedindex, index));   occurencecount++;   if(occurencecount==4) //find 4th occurrence , replaced "new_key_word"   {     output.append("new_key_word")   }   else   {     output.append("key_word")   }   copiedindex = index+("key_word".length);   index = input.indexof("key_word", index+("key_word".length));   if(index==-1)     break; } 

ref: https://docs.oracle.com/javase/7/docs/api/java/lang/string.html#indexof(java.lang.string,%20int)

not sure if had answered question though...