Java for loop isn't terminating in my code -

for reason loop not terminating in capitalizefirstsentence method. set breakpoint @ line , condition (i != -1) unmet, loop should terminate, doesn't!

it works when use (i > 0) condition.

i'm not sure what's going on here.

import javax.swing.joptionpane;  public class sentencecapitalizer {       //main method     public static void main(string[] args) {         string input; //creates string hold keyboard input          //prompt user enter string using joptionpane , set equal input         input = joptionpane.showinputdialog("enter string. ");          //display new string first letter of each sentenced capitalized         joptionpane.showmessagedialog(null, capitalizefirstsentence(input));          //exit program         system.exit(0);     }       //capitalize first letter of each sentence     public static string capitalizefirstsentence(string in)     {         //creates stringbuilder object initiralized string argument "in"         stringbuilder temp = new stringbuilder(in);          //capitalize first letter of string if string length > 0         if (temp.length() > 0)         {             temp.setcharat(0, character.touppercase(temp.charat(0)));         }          //sets equal index of space,          //keep capitalizing first letters of each sentence (loops each time capitlizes letter)         //until end of string         (int = temp.indexof(". ")+1; != -1; i++)         {             //checks spaces , moves index first character of next sentence             while (i < temp.length() && temp.charat(i) == ' ')             {                 i++;             }              //capitalize character             temp.setcharat(i, character.touppercase(temp.charat(i)));              //index end of sentence             = temp.indexof(". ", i);         }          //convert temp string , return our new first-sentenced-capitalized string         return temp.tostring();      }  } 

first, not idea modify loop-controlling variable inside loop - quite hard read , understand such code, , prone errors.

now, example:

for (int = temp.indexof(". ")+1; != -1; i++) 

this means:

• initialize i temp.indexof(". ")+1, >= 0
• terminate if i == -1
• after each iteration, increment i 1

so:

• at start, cycle won't terminate because initialization returns >= 0
• each iteration, loop body set i = temp.indexof(". ", i);, >= -1
• after each iteration, i incremented 1, >= 0
• as i >= 0, never meet condition i == -1 , never terminate