Java string literal automatically interpreted as String object, but how?

Question

What are the mechanics behind Java automatically interpreting string literals as String objects, since there are no overloaded operators and there is no default support for

Answer 1

Basically the compiler rewrites your code.

String x = "Some String";

For concatenation, it is just syntactic sugar for StringBuffer append method, ie this:

z += " with some more in it";

is compiled as:

z = new StringBuffer(z).append(" with some more in it").toString();

Now for a single concat this is an object created and 2 method calls, so if you are building a very long string inside a loop, it is FAR more efficient to write:

StringBuilder buf = new StringBuilder(); // Not synchronized so quicker than StringBuffer
while ( condition is true )
    buf.append(...);
String z = buf.toString();

rather than:

String z = "";
while (condition is true)
   z += "...";

Edit: removed wrong code example...