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java – How to escape % in String.Format?

Posted by: admin March 10, 2020 Leave a comment


I am storing a SQL query in my strings.xml file and I want to use String.Format to build the final string in code. The SELECT statement uses a like, something like this:

SELECT Field1, Field2 FROM mytable WHERE Field1 LIKE '%something%'

In order to format that I replace ‘something’ with %1$s so it becomes:

SELECT Field1, Field2 FROM mytable WHERE Field1 LIKE \'%%1$s%\'

I escape the single quotes with the backslash. However I am not able to escape the % sign.

How can I include a like statement in my strings.xml file?

How to&Answers:

To escape %, you will need to double it up: %%.


To complement the previous stated solution, use:

str = str.replace("%", "%%");


This is a stronger regex replace that won’t replace %% that are already doubled in the input.

str = str.replaceAll("(?:[^%]|\A)%(?:[^%]|\z)", "%%");


I can’t believe that this isn’t a simple solved problem by now, but hey, here’s my stab at it


To sanitise the message before passing it to String.format, you can use the following

Pattern p = Pattern.compile("(?:[^%]|^)(?:(%%)+|)(%)(?:[^%])");
Matcher m1 = p.matcher(log);

StringBuffer buf = new StringBuffer();
while (m1.find())
    m1.appendReplacement(buf, log.substring(m1.start(), m1.start(2)) + "%%" + log.substring(m1.end(2), m1.end()));

// Return the sanitised message
String escapedString = m1.appendTail(buf).toString();

Note that this works with any number of formatting characters, so it will replace % with %%, %%% with %%%%, %%%%% with %%%%%% etc.

It will leave any already escaped characters alone (e.g. %%, %%%% etc.)