Question

为什么输出是空值，三个都 是空值，就是：null,null,null

import java.util.*;
public class Count3Quit {
public static void main(String[] args) {
Collection c = new HashSet();
c.add(new Name("f1","l1"));
c.add(new Name("f2","l2"));
c.add(new Name("f3","l3"));
Iterator i = c.iterator();
while(i.hasNext()) {
Name n = (Name)i.next();
System.out.println(n.getFirstName()+"");
}
}

}
class Name {
String firstName;
String lastName;

Name(String firstName,String lastName) {
firstName = this.firstName;
lastName = this.lastName;
}

public String getFirstName() {
return firstName;
}
}

Answer 1

Name n = (Name)i.next();

这里错了。应该是Name n = (String)i.next();