.replaceAll() method not working correctly

Question

As a bit of background to the problem I load in a text file and then assign a phrase from that text file to become a randomPirateWord, I then change the letters into that text file to become **'s and that works correctly. However when I am asking the user to guess a letter, it doesn't work correctly, if they guess incorrectly then the code works fine but if they guess a letter correctly the code doesn't work properly. I have put the error message below the code:

if (!escape.equalsIgnoreCase("m")){
                    System.out.print(" Type the letter you want to guess: ");
                    char letter = input.nextLine().charAt(0); 

if(m.getRandomPirateWord().contains(letter+"")){
                        System.out.println(m.getRandomPirateWord().replaceAll("*",letter+""));
                    }

Error message:
Exception in thread "main" java.util.regex.PatternSyntaxException: Dangling meta character '*' near index 0
*
^
    at java.util.regex.Pattern.error(Pattern.java:1924)
    at java.util.regex.Pattern.sequence(Pattern.java:2090)
    at java.util.regex.Pattern.expr(Pattern.java:1964)
    at java.util.regex.Pattern.compile(Pattern.java:1665)
    at java.util.regex.Pattern.<init>(Pattern.java:1337)
    at java.util.regex.Pattern.compile(Pattern.java:1022)
    at java.lang.String.replaceAll(String.java:2162)
    at uk.ac.aber.dcs.pirate_hangman.TextBasedGame.runTextBasedGame(TextBasedGame.java:45)
    at uk.ac.aber.dcs.pirate_hangman.Application.runApplication(Application.java:19)
    at uk.ac.aber.dcs.pirate_hangman.Main.main(Main.java:6)

I guess simply googling the error or reading the things that popped up when you typed in the subject was out of the question? Duplicate of: http://stackoverflow.com/questions/917822/tokenizing-error-java-util-regex-patternsyntaxexception-dangling-metacharacter — Brian Roach, Apr 25 '14 at 10:06
BTW, how are you going to decide which `*` to replace? Both `replace()` and `replaceAll()` will replace all the `*`s. — Rohit Jain, Apr 25 '14 at 10:14
I'm really unsure how to determine which * to replace, do you have any recommendations? — user228908, Apr 25 '14 at 14:03

score 5 · Answer 1 · answered Apr 25 '14 at 10:02

5

Use String#replace() instead of String#replaceAll(). The later one uses regex pattern for replacement, where * is a meta-character, and needs to be escaped.

answered Apr 25 '14 at 10:02

Rohit Jain

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Abimaran Kugathasan · Answer 2 · 2014-04-25T10:06:52.400

1

Use the following, You have to escape the * character, since replaceAll() method accepts regular expression as one argument

replaceAll("\\*",letter+"")

edited Apr 25 '14 at 10:06

answered Apr 25 '14 at 10:03

Abimaran Kugathasan

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When I do that it displays the whole word for example The phrase is: ****** * ***** *** I typed in: a And it printed out: you're a bilge rat – user228908 Apr 25 '14 at 10:09
@user228908 : I don't get you. – Abimaran Kugathasan Apr 25 '14 at 10:12
I originally have a word say for example hello, I then replace it into stars so it would become ***** I then ask the user for input of a guess of the letter so for example if they typed h I would want it do display h**** but for some reason if they guess a letter correctly it's displaying the whole word. Hope that makes more sense. – user228908 Apr 25 '14 at 10:14
1

@user228908 Read my comment on your question. I guess you're approaching this problem wrongly. You need to get the actual position of the letter guessed from the original string, and replace the `*` at that position only. Simple `replace()` will not work. – Rohit Jain Apr 25 '14 at 10:18

score 0 · Answer 3 · answered Apr 25 '14 at 10:19

Check out below Example.

import java.io.*;

public class Test{
   public static void main(String args[]){
      String Str = new String("Welcome to Tutorialspoint.com");

      System.out.print("Return Value :" );
      System.out.println(Str.replaceAll("(.*)Tutorials(.*)",
                         "AMROOD" ));
   }
}

Syntax of method :

public String replaceAll(String regex, String replacement)

regex -- the regular expression to which this string is to be matched.
replacement -- the string which would replace found expression.

OUTPUT: AMROOD

Reference : Regex replacement

score -1 · Answer 4 · answered Apr 25 '14 at 10:06

-1

The problem is that * is a reserved character in regexes, so you need to escape it.

replaceAll("\\*",letter+"")

answered Apr 25 '14 at 10:06

Asif Bhutto

3,916
1
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Wasn't me, someone seems to be down voting everyone on this page. – user228908 Apr 25 '14 at 10:15

score -1 · Answer 5 · answered Apr 25 '14 at 10:09

‘*’ symbol is used to identify a group from the regular expression which is the first parameter of ‘replaceAll’ or ‘replaceFirst’ method

1. Using ‘replace’ method: This would be the good choice if you want to replace a string literal and not a pattern.


2. Escaping ‘*’ symbol: If you need to a use regular expression, and your pattern has no groups identified, then you can escape any group identification symbols from your replace string as shown below:



String replaceValue = java.util.regex.Matcher.quoteReplacement("*100");

.replaceAll() method not working correctly

5 Answers5