问题
1 package Demo; 2 3 import java.util.ArrayList; 4 import java.util.Collection; 5 import java.util.HashMap; 6 import java.util.HashSet; 7 import java.util.LinkedList; 8 import java.util.Map; 9 10 import javax.sound.midi.Sequence; 11 12 public class Set { 13 14 public static void main(String[] args) { 15 // TODO Auto-generated method stub 16 Collection c = new ArrayList(); 17 c.add("hello"); 18 // c.add(new Integer("100")); 19 c.add(new Name("a", "b")); 20 System.out.println(c.hashCode()); 21 c.add(new Name("a", "b")); 22 23 // c.remove("hello"); 24 // c.remove(new Integer("100")); 25 System.out.println(c.remove(new Name("a", "b"))); 26 System.out.println(c); 27 28 } 29 } 30 31 class Name extends Object { 32 private String firstname; 33 private String lastname; 34 35 public Name(String firstname, String lastname) { 36 this.firstname = firstname; 37 this.lastname = lastname; 38 } 39 40 public String getFirstname() { 41 return firstname; 42 } 43 44 public String getLastname() { 45 return lastname; 46 } 47 48 public String toString() { 49 return "the firstname is " + firstname + " the last name is " + lastname; 50 } 51 52 public boolean equals(Name a) { 53 return ((this.firstname.equals(a.firstname)) && (this.lastname.equals(a.lastname))); 54 55 } 56 // public boolean equals(Object obj) { 57 // if (obj instanceof Name) { 58 // Name d = (Name) obj; 59 // return (this.firstname.equals(d.firstname)) && 60 // (this.lastname.equals(d.lastname)); 61 // } else 62 // return super.equals(obj); 63 // } 64 65 public int hashCode() { 66 return firstname.hashCode(); 67 } 68 }