How to use MessageFormat.format on a string with symbols { and " in Java

Question

I am trying to use MessageFormat.format() on a string containing the symbols: {

I am fetching this string from my .properties file, as a key value pair like this:

helloWorldString=hello{"hello":"{0}"}

I would like to use the

MessageFormat.format(helloWorldString, "world");

However, this throws an error java.lang.IllegalArgumentException: can't parse argument number: "hello":"%s"

I have also tried:

helloWorldString=hello%7B%22hello%22:%22%s%22%7D

to get the error: java.util.UnknownFormatConversionException: Conversion = '2'

And:

helloWorldString=hello%7B"hello":"%s"%7D

which returns the error: java.util.UnknownFormatConversionException: Conversion = 'D'

Any help on formatting these symbols, with the %s (or an alternative String placeholder) would be greatly appreciated!

Answer 1

Your property file entry should look like this:

helloWorldString='{'"hello":"{0}"'}'

You must escape the { and } symbols which do not enclose arguments with a ' .

From the JavaDocs :

Within a String, a pair of single quotes can be used to quote any arbitrary characters except single quotes. For example, pattern string "'{0}'" represents string "{0}", not a FormatElement. A single quote itself must be represented by doubled single quotes '' throughout a String. For example, pattern string "'{''}'" is interpreted as a sequence of '{ (start of quoting and a left curly brace), '' (a single quote), and }' (a right curly brace and end of quoting), not '{' and '}' (quoted left and right curly braces): representing string "{'}", not "{}".

Answer 2

You're making it up. Have a look at the Javadoc . There is no %s feature in MessageFormat . If you want the result to be "hello world" , the property entry should be

helloWorldString="hello {0}"

Similarly you are making this up as well:

hello%7B%22hello%22:%22%s%22%7D

There is no URL-encoding feature in a .properties file, or in MessageFormat .

Use the documentation.