Replacing substrings in a string using a regular expression group

username

I can't find a proper way to remove substrings that are case-insensitive equal to "null" and replace a huge input data string (with many lines and uses) with an empty string ; as a delimiter.

To simplify, here is an example of what I'm looking for:

input string

Steve;nuLL;2;null\n
null;nullo;nUll;Marc\n
....

expected output

Steve;;2;\n
;nullo;;Marc\n
...

code

Matcher matcher = Pattern.compile("(?i)(^|;)(null)(;|$)").matcher(dataStr);
StringBuffer sb = new StringBuffer();
while (matcher.find()) {
    matcher.appendReplacement(sb, matcher.group(1) + "" + matcher.group(3));
}
return sb.toString();

Can it be solved using regular expressions?

edit:

From the Java code above, I only get the first match ever replaced, but not every appearance in the row and data flow. For whatever reason, the matcher.find()action is only performed once.

Joop Eggen 
return dataStr.replaceAll("(?smi)\\bnull\\b", "");
  • \bis the word boundary.
  • (?i)is an i=case-ignoring command.
  • ( (?s)It's DOT_ALL, which also .matches newlines.)
  • (?m)is MULTI_LINE.

You forgot , all after the appendTaillast replacement . If the string contains multiple lines, add the MULTI_LINE option to reinterpret the ^sum $. See the javadoc Pattern.

while (matcher.find()) {
    matcher.appendReplacement(sb, matcher.group(1) + "" + matcher.group(3));
}
matcher.appendTail(sb);

Or use lambda:

String result = matcher.replaceAll(mr -> mr.group(1) + mr.group(3));

Among them mris the free naming MatchResultoffer replaceAll.

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