5.1.6 String Conversions
There is a string conversion to type String from every other type, including the null type.
5.4 String Conversion
String conversion applies only to the operands of the binary + operator when one of the arguments is a String. In this single special case, the other argument to the + is converted to a String, and a new String which is the concatenation of the two strings is the result of the +. String conversion is specified in detail within the description of the string concatenation + operator (�15.17.1).