What does this java code line mean?

What does this java code line mean?

What does following line returns?
public static java.math.BigDecimal c_balance(java.lang.String,
java.lang.String, long, int);
It is being called by:
@something =
IsNull(convert(numeric,MyQuery.c_balance('123**',10,@id,@year)),0)
I have tried to find information about BigDecimal class, but I could not
find any example with similar structure (with multiple parameters). I will
appreciate any help.