String.replaceAll用于多个字符

Question

I have a line with ^||^ as my delimiter, I am using

int charCount = line.replaceAll("[^" + fileSeperator + "]", "").length();  
if(fileSeperator.length()>1)
{  
    charCount=charCount/fileSeperator.length();
    System.out.println(charCount+"char count between");  
}

This does not work if i have a line that has stray | or ^ as it counts these as well. How can i modify the regex or any other suggestions?

Answer 1

If I understand correctly, what you're really trying to do is count the number of times that ^||^ appears in your String.

If that's the case, you can use:

Matcher m = Pattern.compile(Pattern.quote("^||^")).matcher(line);
int count = 0;
while ( m.find() ) 
    count++;

System.out.println(count + "char count between");

But you really don't need the regex engine for this.

int startIndex = 0;
int count = 0;
while ( true ) {
    int newIndex = line.indexOf(fileDelimiter, startIndex);
    if ( newIndex == -1 ) {
        break;
    } else {
        startIndex = newIndex + 1;
        count++;
    }
}

Answer 2

Certain characters have special meanings in a regular expression, such as ^ and | . These must be escaped with a backslash in order for them to be treated as normal characters and not as special characters. For example, the following regular expression matches all caret ( ^ ) and pipe ( | ) characters (note the backslashes): [\\^\\|]

The Pattern.quote() method can be used to escape all of the special characters in a given String.

String quoted = Pattern.quote("^||^"); //returns "\^\|\|\^";

Also note that a character class only matches one character . Thus, the regex [^\\^\\|\\|\\^] will match all characters except ^ and | , not all characters except the sequence ^||^ . If your intention is to count the number of delimiters ( ^||^ ) in a String, then a better approach might be to use the String.indexOf(String, int) method.

Answer 3

Mark Peters's answer seems better. I edited so my answer won't cause any confusion.

Answer 4

You should replace it like this with proper escaping since your delimiter has all special character of regex:

line.replaceAll("\\^\\|\\|\\^", "");

OR else don't use regex at all and call replace method like this:

line.replace("^||^", "");

Answer 5

Lazy solutions.

Depending on the end goal (the println statement is a little confusing):

int numberOfDelimiters = (line.length() - line.replace(fileSeparator,"").length()) 
                         / fileSeparator.length();

int numberOfNonDelimiterChars = line.replace(fileSeparator,"").length();