Regular expression to replace content between parentheses ()

I tried this code:

string.replaceAll("\\(.*?)","");

But it returns null. What am I missing?开发者_如何学Go

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Try:

string.replaceAll("\\(.*?\\)","");

You didn't escape the second parenthesis and you didn't add an additional "\" to the first one.

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First, Do you wish to remove the parentheses along with their content? Although the title of the question indicates no, I am assuming that you do wish to remove the parentheses as well.

Secondly, can the content between the parentheses contain nested matching parentheses? This solution assumes yes. Since the Java regex flavor does not support recursive expressions, the solution is to first craft a regex which matches the "innermost" set of parentheses, and then apply this regex in an iterative manner replacing them from the inside-out. Here is a tested Java program which correctly removes (possibly nested) parentheses and their contents:

import java.util.regex.*;
public class TEST {
    public static void main(String[] args) {
        String s = "stuff1 (foo1(bar1)foo2) stuff2 (bar2) stuff3";
        String re = "\\([^()]*\\)";
        Pattern p = Pattern.compile(re);
        Matcher m = p.matcher(s);
        while (m.find()) {
            s = m.replaceAll("");
            m = p.matcher(s);
        }
        System.out.println(s);
    }
}

Test Input:

"stuff1 (foo1(bar1)foo2) stuff2 (bar2) stuff3"

Test Output:

"stuff1  stuff2  stuff3"

Note that the lazy-dot-star solution will never work, because it fails to match the innermost set of parentheses when they are nested. (i.e. it erroneously matches: (foo1(bar1) in the example above.) And this is a very commonly made regex mistake: Never use the dot when there is a more precise expression! In this case, the contents between an "innermost" set of matching parentheses consists of any character that is not an opening or closing parentheses, (i.e. Use: [^()]* instead of: .*?).

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Try string.replaceAll("\\(.*?\\)","").

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string.replaceAll("\\([^\\)]*\\)",""); This way you are saying match a bracket, then all non-closing bracket chars, and then a closing bracket. This is usually faster than reluctant or greedy .* matchers.