Replace characters in string if there a multiple of the same character in Java

Question

So I have been learning Java for a little over a month now, and I have a hang man game that I am making but I am having trouble with replacing characters in my string. I have it written so you have two strings, one is called "word" which contains the word to be guessed and the other is called "clone" which is a clone of the word that replaces all the characters with underscores. Then as you guess a letter it checks the string "word" to make sure it contains it, and if it does it replaces the underscore in "clone" with that letter.

while (this.guessesLeft >= 0) {
    char letter;
    int letterIndex;

    getGuess();

    if(this.word.contains(this.letterGuessed)) {
        StringBuilder newString = new StringBuilder(this.clone);

        letterIndex = this.word.indexOf(this.letterGuessed);
        letter = this.word.charAt(letterIndex);

        newString.setCharAt(letterIndex, letter);
        this.clone = newString.toString();
    } else {
        this.guessesLeft--;
    }
    printGameBoard();

}

The problem that I'm having is that if you guess a letter and the string contains two of a character it only shows one. For example, here is my output if the word "burrito" is used.

Guess a letter: r
bur____ 
You have 5 guess left before you die!

Guess a letter: i
bur_i__ 
You have 5 guess left before you die!

Guess a letter: r
bur_i__ 
You have 5 guess left before you die!

How would I edit my game logic so that it if the letter "r" is guessed it puts both R's in the string and not just one? Thanks in advance for the help!

Continuing on your current sample, what should happen if the user provides "i" a second time? Should he lose a try or should nothing happen? — Aaron
– Aaron, Commented Feb 28, 2020 at 13:45
You are only searching for the first instance of that character with indexOf(int ch). There is also a version that accepts the index where to start the search, indexOf(int ch, int fromIndex). You will need to loop that until you come to the end of the string, or there are no more instances of the character (returned index is -1). — vlumi
– vlumi, Commented Feb 28, 2020 at 13:48
@Aaron You are correct the user would lose a turn, I just haven't gotten that far yet haha. I want to get this string problem figured out first. — Tlat
– Tlat, Commented Feb 28, 2020 at 13:51
I feel like a character array would be easier to work with in this case, you wouldn't need StringBuilder or worry about the immutability of String (String.toCharArray() would be the easy way to get it). — Nexevis
– Nexevis, Commented Feb 28, 2020 at 13:53

Bentaye · Accepted Answer · 2020-02-28 14:19:23Z

You need to look for all the indexes for your letter, then replace them all. At the moment you only look for the first one.

To find all indexes, look for a first occurrence of the letter, then if you find one (indexOf returns a positive value), keep looking from that last position using the indexOf(int ch, int fromIndex) method until you have found them all (indexOf returns -1).

Here is an example:

if(this.word.contains(this.letterGuessed)) {

    // look for an occurrence, 
    // if you have one, keep looking for others until you have them all (ie: index = -1)
    List<Integer> indexes = new ArrayList<>();
    int index = this.word.indexOf(this.letterGuessed);
    while (index >= 0) { // <- that will loop until the indexOf returns a -1
        indexes.add(index);
        index = this.word.indexOf(this.letterGuessed, index+1);
    }

    // replace at all the found indexes
    StringBuilder newString = new StringBuilder(this.clone);
    for(int letterIndex : indexes) {
        char c = this.word.charAt(letterIndex);
        newString.setCharAt(letterIndex, c);
    }

    this.clone = newString.toString();

} else {
    this.guessesLeft--;
}

You could also do that in one go, without holding the indexes in a list:

if(this.word.contains(this.letterGuessed)) {
    StringBuilder newString = new StringBuilder(this.clone);

    int index = this.word.indexOf(this.letterGuessed);
    while (index >= 0) {
        char c = this.word.charAt(index);
        newString.setCharAt(index, c);
        index = this.word.indexOf(this.letterGuessed, index+1);
    }

    this.clone = newString.toString();
    System.out.println("clone = " + clone);
} else {
    this.guessesLeft--;
}

Collectives™ on Stack Overflow

Replace characters in string if there a multiple of the same character in Java

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related