Java experience-some mistakes in java

1) instanceof: the class object that implements an interface is also an instance of this interface; a certain class object is also an instance of this super class.

2) The native () modifier method does not have a method body. Use a semicolon ";" instead of braces.

3) main is not a keyword.

4) System. exit (int value), that is, if it is an int, the JVM can exit System. exit (a); it is also legal.

5) &, | can be used on int and boolean, while ^ (exclusive or) can only be used on int.

6) If a class and an interface are defined in the same file and the class is declared as public, nothing can be written before the interface, because the interface can only be modified using public, one file can only have one public access control keyword.
7) under unreachable statement, unreachable statement may occur.
(1) write the statement after the reutrn statement.
(2) write the statement after the throw statement.
(3) define the statement after the break and continue statements.

8) "u10100" // valid, equivalent to 'u101010' and string "0"
9) The shift operator can be used for long int char short byte
10) the class access controller can be public or nothing is added.
11) goto is a reserved word but not a keyword. then is nothing.
12) when the super class type is forcibly converted and assigned to the subclass object, there is no exception in compilation, but an exception will occur during runtime.