How to remove commas at the end of any string

Question

I have Strings "a,b,c,d,,,,, ", ",,,,a,,,,"

I want these strings to be converted into "a,b,c,d" and ",,,,a" respectively.

I am writing a regular expression for this. My java code looks like this

public class TestRegx{
public static void main(String[] arg){
    String text = ",,,a,,,";
    System.out.println("Before " +text);
    text = text.replaceAll("[^a-zA-Z0-9]","");
    System.out.println("After  " +text);
}}

But this is removing all the commas here.

How can write this to achieve as given above?

Answer 1

Use :

text.replaceAll(",*$", "")

As mentioned by @Jonny in comments, can also use:-

text.replaceAll(",+$", "")

Answer 2

Your first example had a space at the end, so it needs to match [, ]. When using the same regular expression multiple times, it's better to compile it up front, and it only needs to replace once, and only if at least one character will be removed (+).

Simple version:

text = text.replaceFirst("[, ]+$", "");

Full code to test both inputs:

String[] texts = { "a,b,c,d,,,,, ", ",,,,a,,,," };
Pattern p = Pattern.compile("[, ]+$");
for (String text : texts) {
    String text2 = p.matcher(text).replaceFirst("");
    System.out.println("Before \"" + text  + "\"");
    System.out.println("After  \"" + text2 + "\"");
}

Output

Before "a,b,c,d,,,,, "
After  "a,b,c,d"
Before ",,,,a,,,,"
After  ",,,,a"