Comments in Java are identical to those in C++. Everything between
/*
and */
is ignored by the compiler, and everything on a single
line after //
is also thrown away. Therefore the following program
is, as far as the compiler is concerned, identical to the first
HelloWorld program.
// This is the Hello World program in Java
class HelloWorld {
public static void main (String args[]) {
/* Now let's print the line Hello World */
System.out.println("Hello World!");
} // main ends here
} // HelloWorld ends here
The /* */
style comments can comment out multiple
lines so they're useful when you want to remove large blocks of
code, perhaps for debugging purposes. //
style
comments are better for short notes of no more than a line. /* */
can also be used in the middle of a line whereas
//
can only be used at the end. However putting a
comment in the middle of a line makes code harder to read and is
generally considered to be bad form.
Comments evaluate to white space, not nothing at all. Thus the following line causes a compiler error:
int i = 78/* Split the number in two*/76;
Java turns this into the illegal line
int i = 78 76;
not the legal line
int i = 7876;
This is also a difference between K&R C and ANSI C.