Why does + work with Strings in Java?

Question

Java can\'t do operator overloading, but + works okay for String and Integer and some other classes. How is this possible?

Answer 1

It works for primitive wrappers like Integer because of autoboxing.

It works for String because that's a special case for concatenating strings:

The Java language provides special support for the string concatenation operator ( + ), and for conversion of other objects to strings. String concatenation is implemented through the StringBuilder(or StringBuffer) class and its append method. String conversions are implemented through the method toString, defined by Object and inherited by all classes in Java. For additional information on string concatenation and conversion, see Gosling, Joy, and Steele, The Java Language Specification.