Specify non-ASCII characters in a file : i18n

You can specify Unicode character with following escape sequence
\u XXXX
where XXXX refer to 4 hexadecimal digits representing value of the UTF-16 code unit.

E.g. a properties file might have the following entries:
s1=hello there

s2=\u3053\u3093\u306b\u3061\u306f

In order to convert a file saved in non-ASCII encoding to ASCII, you can use native2ascii tool, found in <jdk>\bin

non-ASCII

native2ascii [options] [inputfile [outputfile]]

Description
The Java compiler and other Java tools can only process files which contain Latin-1 and/or Unicode-encoded (\udddd notation) characters. native2ascii converts files which contain other character encodings into files containing Latin-1 and/or Unicode-encoded charaters.

If outputfile is omitted, standard output is used for output. If, in addition, inputfile is omitted, standard input is used for input.

Options : 

-reverse

Perform the reverse operation: convert a file with Latin-1 and/or Unicode encoded characters to one with native-encoded characters.

-encoding encoding_name

Specify the encoding name which is used by the conversion procedure. The default encoding is taken from System property file.encoding. The encoding_name string must be taken from the first column of the table of supported encodings in the Supported Encodings document.

-Joption

Pass option to the Java virtual machine, where option is one of the options described on the reference page for the java application launcher. For example, -J-Xms48m sets the startup memory to 48 megabytes.

Source : Here