I think I am late for writing about varargs. The
feature of variable argument has been added in Java 5 since its launch. Still I
will write something about varargs.varargs has been implemented in many languages such as C, C++ etc. These functionality enables to write methods/functions which takes variable length of arguments. For example the popular printf() method in C. We can call printf() method with multiple arguments.
printf("%s",
50);
printf("%d %s
%s", 250, "Hello", "World");
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Varargs was added in Java 5 and the
syntax includes three dots … (also called ellipses). Following is the
syntax of vararg method.
public void testVar(int count,
String... vargs) { }
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Notice the dots … in above code.
That mark the last argument of the method as variable argument. Also the vararg
must be the last argument in the method.
Now let us check simple hello world
varargs code.
public class HelloWorldVarargs
{
public static void main(String
args[]) {
test(215,
"India", "Delhi");
test(147,
"United States", "New York", "California");
}
public static void test(int some,
String... args) {
System.out.print("\n" +
some);
for(String
arg: args) {
System.out.print(",
" + arg);
}
}
}
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In above code, the test() method is
taking variable arguments and is being called from main method with number of
arguments.
So when should you use varargs? As a
client, you should take advantage of them whenever the API offers them.
Important uses in core APIs include reflexion , message formatting, and the new
printf facility. As an API designer, you should use them sparingly, only when
the benefit is truly compelling. Generally speaking, you should not overload a
varargs method, or it will be difficult for programmers to figure out which
overloading gets called.
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