I\'m using the Twitter API and I have the following string that is bugging me Proyecto de ingeniera comercial, actual Profesora de matemáticas \\u0000\\u0000\\u0000\\u
The first argument to replaceAll is a regular expression, and the Java regex engine understands \uNNNN escapes so
json.replaceAll("\\u0000", "")
will search for the regular expression \u0000, which matches instances of the Unicode NUL character (U+0000), not instances of the actual string \u0000. If you want to match the string \u0000 then you need to use the regular expression \\u0000, which in turn means the Java string literal "\\\\u0000"
json.replaceAll("\\\\u0000", "")
Or more simply, use replace (whose first argument is a literal string rather than a regex) instead of replaceAll
json.replace("\\u0000", "")