Cloneable 和 clone()的总结和使用
一.Cloneable 的用途
Cloneable和Serializable一样都是标记型接口，它们内部都没有方法和属性，implements Cloneable表示该对象能被克隆，能使用Object.clone()方法。如果没有implements Cloneable的类调用Object.clone()方法就会抛出CloneNotSupportedException。

二.克隆的分类
(1)浅克隆（shallow clone），浅拷贝是指拷贝对象时仅仅拷贝对象本身和对象中的基本变量，而不拷贝对象包含的引用指向的对象。
(2)深克隆（deep clone），深拷贝不仅拷贝对象本身，而且拷贝对象包含的引用指向的所有对象。

举例区别一下：对象A1中包含对B1的引用，B1中包含对C1的引用。浅拷贝A1得到A2，A2中依然包含对B1的引用，B1中依然包含对C1的引用。深拷贝则是对浅拷贝的递归，深拷贝A1得到A2，A2中包含对B2（B1的copy）的引用，B2中包含对C2（C1的copy）的引用。

三.克隆的举例
要让一个对象进行克隆，其实就是两个步骤：
1. 让该类实现java.lang.Cloneable接口；
2. 重写（override）Object类的clone()方法。
Java代码:

1. public class Wife implements Cloneable {
2. private int id;
3. private String name;
5. public int getId() {
6. return id;
7. }
9. public void setId(int id) {
10. this.id = id;
11. }
13. public String getName() {
14. return name;
15. }
17. public void setName(String name) {
18. this.name = name;
19. }
21. public Wife(int id,String name) {
22. this.id = id;
23. this.name = name;
24. }
26. @Override
27. public int hashCode() {//myeclipse自动生成的
28. final int prime = 31;
29. int result = 1;
30. result = prime * result + id;
31. result = prime * result + ((name == null) ? 0 : name.hashCode());
32. return result;
33. }
35. @Override
36. public boolean equals(Object obj) {//myeclipse自动生成的
37. if (this == obj)
38. return true;
39. if (obj == null)
40. return false;
41. if (getClass() != obj.getClass())
42. return false;
43. Wife other = (Wife) obj;
44. if (id != other.id)
45. return false;
46. if (name == null) {
47. if (other.name != null)
48. return false;
49. } else if (!name.equals(other.name))
50. return false;
51. return true;
52. }
54. @Override
55. public Object clone() throws CloneNotSupportedException {
56. return super.clone();
57. }
59. /**
60. * @param args
61. * @throws CloneNotSupportedException
62. */
63. public static void main(String[] args) throws CloneNotSupportedException {
64. Wife wife = new Wife(1,"wang");
65. Wife wife2 = null;
66. wife2 = (Wife) wife.clone();
67. System.out.println("class same="+(wife.getClass()==wife2.getClass()));//true
68. System.out.println("object same="+(wife==wife2));//false
69. System.out.println("object equals="+(wife.equals(wife2)));//true
70. }
71. }

四.浅克隆的举例 Java代码:

1. public class Husband implements Cloneable {
2. private int id;
3. private Wife wife;
5. public Wife getWife() {
6. return wife;
7. }
9. public void setWife(Wife wife) {
10. this.wife = wife;
11. }
13. public int getId() {
14. return id;
15. }
17. public void setId(int id) {
18. this.id = id;
19. }
21. public Husband(int id) {
22. this.id = id;
23. }
25. @Override
26. public int hashCode() {//myeclipse自动生成的
27. final int prime = 31;
28. int result = 1;
29. result = prime * result + id;
30. return result;
31. }
33. @Override
34. protected Object clone() throws CloneNotSupportedException {
35. return super.clone();
36. }
38. @Override
39. public boolean equals(Object obj) {//myeclipse自动生成的
40. if (this == obj)
41. return true;
42. if (obj == null)
43. return false;
44. if (getClass() != obj.getClass())
45. return false;
46. Husband other = (Husband) obj;
47. if (id != other.id)
48. return false;
49. return true;
50. }
52. /**
53. * @param args
54. * @throws CloneNotSupportedException
55. */
56. public static void main(String[] args) throws CloneNotSupportedException {
57. Wife wife = new Wife(1,"jin");
58. Husband husband = new Husband(1);
59. Husband husband2 = null;
60. husband.setWife(wife);
61. husband2 = (Husband) husband.clone();
62. System.out.println("husband class same="+(husband.getClass()==husband2.getClass()));//true
63. System.out.println("husband object same="+(husband==husband2));//false
64. System.out.println("husband object equals="+(husband.equals(husband)));//true
65. System.out.println("wife class same="+(husband.getWife().getClass()==husband2.getWife().getClass()));//true
66. System.out.println("wife object same="+(husband.getWife()==husband2.getWife()));//true
67. System.out.println("wife object equals="+(husband.getWife().equals(husband.getWife())));//true
68. }
69. }

五.深克隆的举例
如果要深克隆，需要重写（override）Object类的clone()方法，并且在方法内部调用持有对象的clone()方法；注意如下代码的clone()方法Java代码:

1. public class Husband implements Cloneable {
2. private int id;
3. private Wife wife;
5. public Wife getWife() {
6. return wife;
7. }
9. public void setWife(Wife wife) {
10. this.wife = wife;
11. }
13. public int getId() {
14. return id;
15. }
17. public void setId(int id) {
18. this.id = id;
19. }
21. public Husband(int id) {
22. this.id = id;
23. }
25. @Override
26. public int hashCode() {//myeclipse自动生成的
27. final int prime = 31;
28. int result = 1;
29. result = prime * result + id;
30. return result;
31. }
33. @Override
34. protected Object clone() throws CloneNotSupportedException {
35. Husband husband = (Husband) super.clone();
36. husband.wife = (Wife) husband.getWife().clone();
37. return husband;
38. }
40. @Override
41. public boolean equals(Object obj) {//myeclipse自动生成的
42. if (this == obj)
43. return true;
44. if (obj == null)
45. return false;
46. if (getClass() != obj.getClass())
47. return false;
48. Husband other = (Husband) obj;
49. if (id != other.id)
50. return false;
51. return true;
52. }
54. /**
55. * @param args
56. * @throws CloneNotSupportedException
57. */
58. public static void main(String[] args) throws CloneNotSupportedException {
59. Wife wife = new Wife(1,"jin");
60. Husband husband = new Husband(1);
61. Husband husband2 = null;
62. husband.setWife(wife);
63. husband2 = (Husband) husband.clone();
64. System.out.println("husband class same="+(husband.getClass()==husband2.getClass()));//true
65. System.out.println("husband object same="+(husband==husband2));//false
66. System.out.println("husband object equals="+(husband.equals(husband)));//true
67. System.out.println("wife class same="+(husband.getWife().getClass()==husband2.getWife().getClass()));//true
68. System.out.println("wife object same="+(husband.getWife()==husband2.getWife()));//false
69. System.out.println("wife object equals="+(husband.getWife().equals(husband.getWife())));//true
70. }
71. }

但是也有不足之处，如果Husband内有N个对象属性，突然改变了类的结构，还要重新修改clone()方法。解决办法：可以使用Serializable运用反序列化手段，调用java.io.ObjectInputStream对象的 readObject()方法。

参考java创建对象的第四种方法：
http://www.software8.co/wzjs/java/2881.html