When is an unassigned expression a valid statement?

Question

I\'ve read Oracle\'s expressions tutorial and couldn\'t understand this.

It is well known that the following line of code is valid Java syntax:

new O         


        

Answer 1

Line containing only

new Object(); 

or to be more precise

new SomeClass(); 

is acceptable, because code of SomeClass() constructor may be all we want.

But in case of lines containing only

"foo";

or

2;//or (2+3);

compiler knows that beside creating/reusing String literal or integer literal this code doesn't do anything else, which means it is probably some kind of programmer mistake so compiler can't accept it.