Why was org.apache.common.lang3 StringEscapeUtils deprecated?

The class was moved from package

org.apache.commons.lang3

to

org.apache.commons.text

You can replace the deprecated library easily:

In your build.gradle:

implementation 'org.apache.commons:commons-text:1.9'

And in your class using StringEscapeUtils make sure you import the correct class:

import org.apache.commons.text.StringEscapeUtils;

1.9 is currently the newest version (last checked February 24th 2021) but you can check the versions at maven:
https://mvnrepository.com/artifact/org.apache.commons/commons-text

From Commons-lang 3.6 release notes:

The Apache Commons Community has recently set up the Commons Text component
as a home for algorithms working on strings. For this reason most of the string
focused functionality in Commons Lang has been deprecated and moved to
Commons Text. This includes:

o All classes in the org.apache.commons.lang3.text and the
org.apache.commons.lang3.text.translate packages
o org.apache.commons.lang3.StringEscapeUtils
o org.apache.commons.lang3.RandomStringUtils
o The methods org.apache.commons.lang3.StringUtils.getJaroWinklerDistance and
org.apache.commons.lang3.StringUtils.getLevenshteinDistance

For more information see the Commons Text website:

http://commons.apache.org/text

Do below steps

• Add below dependency to your pom.xml (if using maven)
  <dependency>
  <groupId>org.apache.commons</groupId>
  <artifactId>commons-text</artifactId>
  <version>1.4</version>
  <dependency>

• Import correct package as below
  import org.apache.commons.text.StringEscapeUtils;

• There is no such method unescapeHtml() in this class anymore, instead its two
  variations are available
  unescapeHtml3() and unescapeHtml4()
• Use unescapeHtml3() to unescape Html 3.0 characters
• Use unescapeHtml4() to unescape Html 4.0 characters

Per the deprecation listing, it was moved to a new project — commons-text