how to decode html codes using Java? [duplicate]

Answer 1

Use methods provided by Apache Commons Lang

import org.apache.commons.lang.StringEscapeUtils;
// ...
String afterDecoding = StringEscapeUtils.unescapeHtml(beforeDecoding);

Answer 2

Do not try to solve everything by regexp.

While you can do some parts - such as replacing entities, the much better approach is to actually use a (robust) HTML parser.

See this question: RegEx match open tags except XHTML self-contained tags for why this is a bad idea to do with the regexp swiss army chainsaw. Seriously, read this question and the top answer, it is a stack overflow highlight!

Chuck Norris can parse HTML with regex.

The bad news is: there is more than one way to encode characters.

https://en.wikipedia.org/wiki/Character_encodings_in_HTML

For example, the character 'λ' can be represented as λ, λ or λ

And if you are really unlucky, some web site relies on some browsers capabilities to guess character meanings. ™ for example is not valid, yet many browsers will interpret it as ™.

Clearly it is a good idea to leave this to a dedicated library instead of trying to hack a custom regular expression yourself.

So I strongly recommend:

• Feed string into a robust HTML parser
• Get parsed (and fully decoded) string back