Regex: PatternSyntaxException: Illegal repetition

Question

I am not good at regex and I am trying to use java.lang.String replaceAll() method with code segments as follows

A is:

public class method3 {

    public static int addTwoNumbers(int one, int two){
        return one+two;
    }

    public static void main (String[] args){
        int total = addTwoNumbers(1, 3);
        System.out.println(total);
    }
}

to replace with B

null
public class method3 {
    /* some writting */
    public static int addTwoNumbers(int one, int two){
        return one+two;
    }
    /*more text*/
    public static void main (String[] args){
        int total = addTwoNumbers(1, 3);
        System.out.println(total);
    }//end of 
}

And this is giving me the following error

java.util.regex.PatternSyntaxException: Illegal repetition

Im guessing this has something to do with the /**/ characters?

How do you sort this and is there any other characters i need to look out for?

EDIT: This is the error message

Exception in thread "AWT-EventQueue-0" java.util.regex.PatternSyntaxException: Illegal repetition near index 25
null
public class method2 {

    public static int addTwoNumbers(int one, int two){
        return one+two;
    }

    public static void main (String[] args){
        int total = addTwoNumbers(1, 3);
        System.out.println(total);
    }
}


                         ^
    at java.util.regex.Pattern.error(Pattern.java:1924)
    at java.util.regex.Pattern.closure(Pattern.java:3104)
    at java.util.regex.Pattern.sequence(Pattern.java:2101)
    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)
    ....

call to replaceAll()

        String a = readFile(directoryToAddFile,startOfCode, endOfCode);
        String b = textarea.getText().toString();
        String content = IOUtils.toString(new FileInputStream(directoryToAddFile));
        content = content.replaceAll(a, b);
        IOUtils.write(content, new FileOutputStream(directoryToAddFile));

It would help if you'd show the code which is failing. Yes, * has a special meaning in regular expressions... but it may be that regexes aren't the best approach here anyway. — Jon Skeet
– Jon Skeet, Commented Sep 4, 2012 at 17:38
where are you using patterns at all? I only see System.out.println and one+two. — gexicide
– gexicide, Commented Sep 4, 2012 at 17:41
the code is the same i am trying to replace just that it has some omments in it... this is just a simple example — flexinIT
– flexinIT, Commented Sep 4, 2012 at 17:42

FThompson · Accepted Answer · 2012-09-04 17:50:51Z

10

Currently, your code attempts to analyze the "to replace" string as a regex.

To replace a string literally rather than as a regex, you can use Pattern#quote(String).

content = content.replaceAll(Pattern.quote(a), b);

Also, as a side note, you might find String#replace(CharSequence, CharSequence) more appropriate than replaceAll in this situation.

answered Sep 4, 2012 at 17:50

FThompson

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3 Comments

flexinIT Over a year ago

I have tried both your suggestions about yet none of them work(well not working), I am not getting the error no more but it is not replacing any of the text for the content

FThompson Over a year ago

In that case, the replace methods simply aren't finding your string in the other string. That's a different question altogether though, so if you wish to ask it, create a new question rather than editing this one. However, that's an issue easily solvable through some simple debugging.

flexinIT Over a year ago

yes, there was white space at the end of one of the strings so after i .trim() on the string it worked, cheers

BlackVegetable · Accepted Answer · 2012-09-04 17:51:52Z

0

Your issue is likely stemming from not escaping several of the characters in what you are trying to replace, as well as what you are trying to replace it with. Regex may not be the tool you want to use here. From www.regular-expressions.info, the characters to be aware of are []\^$.|?*+()

Read up on that website to see the uses/limitations of regex.

answered Sep 4, 2012 at 17:51

BlackVegetable

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