The message is:
Main.java:14: error: ')' expected
System.out.println(1 ++ 2);
^
The 1 ++ 2 statement is parsed as 1 followed by ++ followed by 2. This is interpreted as 1++ and 2 creating a syntax error (and not an unexpected type error; in fact, you will get the same error if you used variables e.g. i ++ j).
The 1 + + 2 statement on the other hand is parsed as 1 followed by + followed by +2 which compiles as expected. The space between the two operators separates the two operators.
