Java – Replace text in StringBuilder via regex

javaregexstringbuilder

I would like to replace some texts in StringBuilder. How to do this?

In this code I got java.lang.StringIndexOutOfBoundsException at line with matcher.find():

StringBuilder sb = new StringBuilder(input);
Pattern pattern = Pattern.compile(str_pattern);
Matcher matcher = pattern.matcher(sb);
while (matcher.find())
  sb.replace(matcher.start(), matcher.end(), "x");

Best Answer

Lets have a StringBuilder w/ 50 total length and you change the first 20chars to 'x'. So the StringBuilder is shrunk by 19, right - however the initial input pattern.matcher(sb) is not altered, so in the end StringIndexOutOfBoundsException.

Related Solutions

Java – How to assert that a certain exception is thrown in JUnit 4 tests

It depends on the JUnit version and what assert libraries you use.

For JUnit5 and 4.13 see answer https://stackoverflow.com/a/2935935/2986984
If you use assertJ or google-truth, see answer https://stackoverflow.com/a/41019785/2986984

The original answer for JUnit <= 4.12 was:

@Test(expected = IndexOutOfBoundsException.class)
public void testIndexOutOfBoundsException() {

    ArrayList emptyList = new ArrayList();
    Object o = emptyList.get(0);

}

Though answer https://stackoverflow.com/a/31826781/2986984 has more options for JUnit <= 4.12.

Reference :

JUnit Test-FAQ

Python – Escaping regex string

Use the re.escape() function for this:

4.2.3 re Module Contents

escape(string)

Return string with all non-alphanumerics backslashed; this is useful if you want to match an arbitrary literal string that may have regular expression metacharacters in it.

A simplistic example, search any occurence of the provided string optionally followed by 's', and return the match object.

def simplistic_plural(word, text):
    word_or_plural = re.escape(word) + 's?'
    return re.match(word_or_plural, text)

Best Answer

Related Solutions

Java – How to assert that a certain exception is thrown in JUnit 4 tests

Python – Escaping regex string

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