Replacing the parts of a string with a given index position of the actual string Java -

i'm little short handed on understanding how can proceed code. i'm doing hang-man game , made copy of the actual word. copy replaced blank spaces , i'm wondering how can replace blank spaces when player correctly guesses word

        while(!gameover && difficulty.equals("1") || difficulty.equals("3") || difficulty.equals("2")){             system.out.println(userword);             system.out.print("enter guess! make sure it's singular letter only!: ");             choice = inputs.nextline().tolowercase();             while(choice.length()==1){                  int check1 = lettersguessed.indexof(choice);                 if (check1 == -1){                     //system.out.println("b");                     lettersguessed = lettersguessed+letter;                     if (word.indexof(choice) == -1) {                         mistakes++; //mistakes - add on here                         system.out.println("you guessed wrong letter! keep guessing!");                         break;                     }                     else{                         system.out.println("you've guessed right letter!");                         string jake = word.indexof(choice);                          userword = userword.replace(userword,jake);                         break; 

and game loop. in else statement @ bottom don't know how i'm suppose work out. @ bottom can index position of player's guess in actual word.

strings immutable in java. you'll want construct new string.

one way this:

char characterguessed = choice.charat(0); stringbuilder builder = new stringbuilder(); for(int = 0; < word.length(); i++) {     if(word.charat(i) == characterguessed) {       builder.append(characterguessed);     } else {       builder.append(userword.charat(i));     } } userword = builder.tostring();