This is a built-in template used for replacing a string concatenation (e.g. String s = "Hello " + name;) with an internationalized Java code expression (e.g. String s = MessageFormat.format(​myResourceBundle.getString(​"hello.0"), name);).
The template is editable. Along with Java expressions and comments, you can also use predefined variables that will be then expanded into the corresponding values.
Predefined variables will take the following values:
${RESOURCE_BUNDLE}   Expression of type java.util.ResourceBundle, instance of which is available in this context.
${PARAMETERS}   Variables used in the string concatenation, usually passed as arguments to the internationalized expression.
${PROPERTY_KEY}   Property key name which is defined in the corresponding properties file. Typically it is the value that is used for ResourceBundle.getString() method parameter.
${PROPERTY_VALUE}   Property value which is defined in the corresponding properties file. This is the original Java string literal value.