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Thread: class String replaceAll does not behave as i expected

  1. #1
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    Default class String replaceAll does not behave as i expected

    The situation : I have a string and if a word is considered to be a mistake it has to be replaced by "SPELLING_MISTAKE".How do i resolve if a word is a mistake or not?I have a string array with all the correct words.So when i trace the wrong word the progam behaves good and reaches the line where the replacement is meant to be done.But no replacement is done :/ Why?What i am missing?

    package essaycorrection;
     
    public class Phrase {
     
        /**
         * **************************Variables-fields****************************
         */
        private int noOfWords;
        private String content;
        private static final String[] correctWords = {"All", "Work", "And", "No", "Play",
            "Makes", "Jack", "A", "Dull", "Boy"};
        private static final String[] wrongWords = {"Samaras", "Theodor", "George", "Kostoula",
            "Charalampos", "Pokemon", "Lapras", "Kahn", "Charizard", "Skoupi"};
     
        /**
         * **************************Constructor****************************
         */
        public Phrase(int N) {
            content = "";
            noOfWords = 1 + (int) (Math.random() * N);//numbers from [1,N]
            int select;//pick correct or wrong word
            for (int i = 0; i < noOfWords; i++) {
                select = (int) (Math.random() * 2);
                if (select == 1) {
                    content += correctWords[(int) (Math.random() * noOfWords)] + " ";
                } else {
                    content += wrongWords[(int) (Math.random() * noOfWords)] + " ";
                }
            }
            System.out.println("I just composed a phrase with content : " + content + ".");
        }
     
        /**
         * **************************Accessors****************************
         */
        public int getNoOfWords() {
            return noOfWords;
        }
     
        public String getContent() {
            return content;
        }
     
        public String[] getCorrectWords() {
            return correctWords;
        }
     
        public String[] getWrongWords() {
            return wrongWords;
        }
     
        /**
         * **************************Methods****************************
         */
        void spellCorrect() {
            String temp = "";//holds a word at the time in order to check the correctness
            char letter;
            boolean mistake;
            int i = 0;
            while (i < content.length()) {
                if ((letter = content.charAt(i)) != ' ') {
                    temp += letter;
                } else {
                    mistake = true;
                    for (int j = 0; j < correctWords.length; j++) {
                        if ((temp.compareToIgnoreCase(correctWords[j])) == 0) {
                            mistake = false;
                        }
                    }
                    if (mistake) {System.out.println("edw1 "+temp );
                        content.replaceAll(temp, "SPELLING_MISTAKE");
                    }
                    temp="";
                }
                i++;
            }
     
        }
     
        public void print()
        {
            System.out.println(content+".");
        }
    }

    in main
            Phrase p = new Phrase(5);
            p.spellCorrect();
            p.print();

    and the output
    I just composed a phrase with content : Samaras Samaras Samaras .
    edw1 Samaras
    edw1 Samaras
    edw1 Samaras
    Samaras Samaras Samaras .
    BUILD SUCCESSFUL (total time: 0 seconds)

    Also tried replaceFirst but no change in output!


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: class String replaceAll does not behave as i expected

    where is the main() method for testing the code?

    If you are only having problems with the replaceAll() method, write a short simple program that uses that method many different ways to see how the method works. All the extra logic in what you have posted does not help solving the problem learning how to use replaceAll().
    When you get the technique for using the replaceAll() method then you can work on the logic in the posted code.
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: class String replaceAll does not behave as i expected

    Quote Originally Posted by Samaras View Post
    ...What i am missing?...
    replaceAll does not replace anything in the existing String (It can't, because Strings are immutable.) What it does is that it creates a brand new String with replacement as directed.

    Try the following in spellCorrect() to see what the program is seeing:
                    if (mistake) {
                        System.out.println("edw1 "+temp );
                        System.out.printf("    Before correction: <%s>\n", content);
                        content.replaceAll(temp, "SPELLING_MISTAKE");
                        System.out.printf("    After  correction: <%s>\n", content);
                    }

    Then try the following and see what happens. (Get ready to hit Ctrl-C or the "Stop" button or whatever you need to do to make a runaway program stop running away.)
                    if (mistake) {
                        System.out.println("edw1 "+temp );
                        System.out.printf("   Before correction: <%s>\n", content);
                        content = content.replaceAll(temp, "SPELLING_MISTAKE");
                        System.out.printf("   After  correction: <%s>\n", content);
                    }


    Cheers!

    Z
    Last edited by Zaphod_b; August 19th, 2012 at 10:25 AM.

  4. #4
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    Default Re: class String replaceAll does not behave as i expected

    @Norm i wrote the lines of main that are invoke the method
    @Zaphod_b the answer was Strings are immutable ( unlike the StringBuilder Class).Hitting stop run was also needed.I am going to fix it now!Thank you both.

    PS-Zaphod_b your name is awesome ,it reminds me of Zapdos(this is a pokemon ) from when i was a kid.

  5. #5
    Super Moderator Norm's Avatar
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    Default Re: class String replaceAll does not behave as i expected

    i wrote the lines of main that are invoke the method
    Where is the main() method for testing? I don't see where the code is that can be compiled for testing.
    Can you provide one for testing?
    If you don't understand my answer, don't ignore it, ask a question.

  6. #6
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    Default Re: class String replaceAll does not behave as i expected

    Quote Originally Posted by Samaras View Post
    I am going to fix it now!
    Solved! I post it in order other people face the same problem
    void spellCorrect() {
            String temp = "";//holds a word at the time in order to check the correctness
            char letter;
            boolean mistake;
            int i = 0;
            while (i < content.length()) {
                if ((letter = content.charAt(i)) != ' ') {
                    temp += letter;
                } else {
                    mistake = true;
                    for (int j = 0; j < correctWords.length; j++) {
                        if ((temp.compareToIgnoreCase(correctWords[j])) == 0) {
                            mistake = false;
                        }
                    }
                    if (mistake) {
                        content=content.replaceAll(temp, "SPELLING_MISTAKE");
                        while ((letter = content.charAt(i)) != ' ') {
                            i++;
                        }
                    }
                    temp="";
                }
                i++;
            }
     
        }

    Quote Originally Posted by Norm View Post
    Where is the main() method for testing? I don't see where the code is that can be compiled for testing.
    Can you provide one for testing?
    Oh,i did that in order not to make you tired of reading code.I solve it now

  7. #7
    Super Moderator Norm's Avatar
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    Default Re: class String replaceAll does not behave as i expected

    That's fine if you don't want anyone to help by compiling and testing the code.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: class String replaceAll does not behave as i expected

    Quote Originally Posted by Norm View Post
    That's fine if you don't want anyone to help by compiling and testing the code.
    All i wanted is to make your life easier :/ I understand that i did not succeed in it.Now you told i'll keep that in mind

  9. #9
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    Default Re: class String replaceAll does not behave as i expected

    Leaving out code that can have an impact on how the program executes doesn't make it easier to understand a problem. Seeing all of the code so there are no doubts about what else could be happening makes it easier. Since most beginners don't know what is important and what is not important, posting full code for testing is better.
    If you don't understand my answer, don't ignore it, ask a question.

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