which objects use heap space?

[Li Li]

I have a class without any space allocation, but by using jmap -heap,
I found about 400K space is used. is it allocated by jvm?

public class TestGc2 {
public static void main(String[] args) throws Exception {
waitEnter("waiting gc...");
waitEnter("before exit");
}
public static void test() throws Exception{

}
private static void waitEnter(String s) throws IOException{
System.out.println(s);
System.in.read();
System.gc();
}
}