Remove spaces and special characters from string

Question

How can I format a string phone number to remove special characters and spaces?

The number is formatted like this [phone]

I am trying to make it look like this: 1231231111

So far I have this:

phone = phone.replaceAll("\\s","");
phone = phone.replaceAll("(","");

The first line will remove the spaces. Then I am having trouble removing the parentheses. Android studio underlines the "(" and throws the error unclosed group.

Solution 1

You can remove everything but the digits:

phone = phone.replaceAll("[^0-9]","");

Solution 2

To remove all non-digit characters you can use

replaceAll("\\D+",""); \\ \D is negation of \d (where \d represents digit) 

If you want to remove only spaces, ( and ) you can define your own character class like

replaceAll("[\\s()]+","");

Anyway your problem was caused by fact that some of characters in regex are special. Among them there is ( which can represent for instance start of the group. Similarly ) can represent end of the group.

To make such special characters literals you need to escape them. You can do it many ways

• "\\(" - standard escaping in regex
• "[(]" - escaping using character class
• "\\Q(\\E" - \Q and \E create quote - which means that regex metacharacters in this area should be treated as simple literals
• Pattern.quote("(")) - this method uses Pattern.LITERAL flag inside regex compiler to point that metacharacters used in regex are simple literals without any special meaning

Solution 3

You need to escape the ( as it denotes a metacharacter (start of a group) in regular expressions. Same for ).

phone = phone.replaceAll("\\(","");