Null return value
1.Using a null return value indicates that the code has ended, which will end the function.
2.After using a null return value, the statement after the return statement will not be executed, and the compilation will report an error.

1.Using a null return value indicates that the code has ended, which will end the function.
2.After using a null return value, the statement after the return statement will not be executed, and the compilation will report an error.
