What does this mean in java ?

Question

ERROR : incompatible types: void cannot be converted to double

public class otherCLASS
{
static void DIVIDEby2(double divide)

{
divide=divide/2;
System.out.println(divide) ;
}

But when write the code like this,then there is no error

public class otherCLASS
{
static double DIVIDEby2(double divide)

{
divide=divide/2;
return divide ;
}

EDIT :
main method

public static void main(String[]args)
{
double y = 100;
double w = DIVIDEby2(y);
System.out.println(y);
System.out.println(w);
}

Answer 1

void method return nothing..
so,when u use the first method,and want to assign it to double w,u try to cast/convert "nothing" to a double.
since there is nothing to convert,it gives error

but the second one returns double,so it runs normally

Answer 2

how did u use that method in main?

Answer 3

@Lily Mea
Thanks.