Java Regular Expression remove Matches from String

Question

I'm trying to figure out how to remove the found matches from my String. So my Code sample currently looks like this:

public void checkText() {
    String helper = "985, 913, 123, SomeotherText, MoreText, MoreText";
    Pattern pattern = Pattern.compile("\\b\\d{3}");
    Matcher matcher = pattern.matcher(helper);
    while (matcher.find()) {
        String newtext = "Number: " + matcher.group() + "\n"+ newtext;
        helper.replaceAll(matcher.group(),"");
    }
    newtext = newtext + "________________\n"+ helper;
    editText.setText(newtext);
}

So my input string is: 985, 913, 123, SomeotherText, MoreText, MoreText

After running the code what I would like to see is this:

Number: 985
Number: 913
Number: 123
________________________
SomeotherText, MoreText, MoreText

Anyone can tell me whats wrong in my current code?

You're replacing only numbers and expect commas to be replaced as well. You should add them to your regex as well. — DDovzhenko
– DDovzhenko, Commented Jul 11, 2019 at 12:31

The fourth bird · Accepted Answer · 2019-07-11 12:47:01Z

2

There are a few things you could update in the code:

You should set the return of the replacement to helper
If you only replace with an empty string, your string will start with , , , in the replacement leaving the comma's and the follwing space
You might initialize the variable String newtext = "";

See a Java demo

Your code might look like:

String helper = "985, 913, 123, SomeotherText, MoreText, MoreText";
Pattern pattern = Pattern.compile("\\b\\d{3}");
Matcher matcher = pattern.matcher(helper);
String newtext = "";

while (matcher.find()) {
    newtext = "Number: " + matcher.group() + "\n"+ newtext;
    helper = helper.replaceAll(matcher.group() + ", ","");
}
newtext = newtext + "________________\n"+ helper;
System.out.println(newtext);

Result:

Number: 123
Number: 913
Number: 985
________________
SomeotherText, MoreText, MoreText

edited Jul 11, 2019 at 12:47

answered Jul 11, 2019 at 12:30

The fourth bird

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Comments

Eritrean · Accepted Answer · 2019-07-11 12:49:41Z

0

Since you are already using the Matcher class you can also use the method Matcher.appendReplacement for the replacement:

public void checkText() {
    String helper = "985, 913, 123, SomeotherText, MoreText, MoreText";
    Pattern pattern = Pattern.compile("\\b\\d{3}, ");
    Matcher matcher = pattern.matcher(helper);
    StringBuffer sb = new StringBuffer();
    while (matcher.find()) {
        System.out.println("Number:"+matcher.group());
        matcher.appendReplacement(sb, "");
    }
    matcher.appendTail(sb);
    System.out.println(sb.toString());
}

answered Jul 11, 2019 at 12:49

Eritrean

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