1.最终调用的是一个JNI方法，即java本地方法，加快速度
2.使用clone方法，分为浅复制、深复制，这里直接使用网上抄来的案例来说明吧：
说明：
1）为什么我们在派生类中覆盖Object的clone()方法时，一定要调用super.clone()呢？在运行时刻，Object中的clone()识别你要复制的是哪一个对象，然后为此对象分配空间，并进行对象的复制，将原始对象的内容一一复制到新对象的存储空间中。
2）继承自java.lang.Object.clone()方法是浅层复制。一下代码可以证明之：
1 public class Student implements Cloneable { 2 private String name; 3 private int age; 4 private Professor pro; 5 public Student(){} 6 public Student(String name,int age,Professor pro){ 7 this.name=name; 8 this.age=age; 9 this.pro=pro; 10 } 11 public Object clone(){ 12 Object o=null; 13 try { 14 //Object中的clone()识别出你要复制的是哪一个对象。 15 o=super.clone(); 16 } catch (CloneNotSupportedException e) { 17 System.out.println(e.toString()); 18 } 19 return o; 20 } 21 public String getName() { 22 return name; 23 } 24 public void setName(String name) { 25 this.name = name; 26 } 27 public int getAge() { 28 return age; 29 } 30 public void setAge(int age) { 31 this.age = age; 32 } 33 public Professor getPro() { 34 return pro; 35 } 36 public void setPro(Professor pro) { 37 this.pro = pro; 38 } 39 } 40 class Professor{ 41 private String name; 42 private int age; 43 public Professor(){} 44 public Professor(String name,int age){ 45 this.name=name; 46 this.age=age; 47 } 48 public String getName() { 49 return name; 50 } 51 public void setName(String name) { 52 this.name = name; 53 } 54 public int getAge() { 55 return age; 56 } 57 public void setAge(int age) { 58 this.age = age; 59 } 60 }
1 public class StudentTest { 2 public static void main(String[] args) { 3 Professor p=new Professor("wangwu",50); 4 Student s1=new Student("zhangsan",18,p); 5 Student s2=(Student)s1.clone(); 6 s2.getPro().setName("maer"); 7 s2.getPro().setAge(40); 8 System.out.println("name="+s1.getPro().getName() 9 +",age="+s1.getPro().getAge()); 10 //name=maer,age=40 11 } 12 }
那么我们如何实现深层复制的克隆，即在修改s2.Professor时不影响s1.Professor？代码改进如下：
1 public class Student implements Cloneable { 2 private String name; 3 private int age; 4 Professor pro; 5 public Student(){} 6 public Student(String name,int age,Professor pro){ 7 this.name=name; 8 this.age=age; 9 this.pro=pro; 10 } 11 public Object clone(){ 12 Student o=null; 13 try { 14 //Object中的clone()识别出你要复制的是哪一个对象。 15 o=(Student)super.clone(); 16 } catch (CloneNotSupportedException e) { 17 System.out.println(e.toString()); 18 } 19 o.pro=(Professor)pro.clone(); 20 return o; 21 } 22 public String getName() { 23 return name; 24 } 25 public void setName(String name) { 26 this.name = name; 27 } 28 public int getAge() { 29 return age; 30 } 31 public void setAge(int age) { 32 this.age = age; 33 } 34 public Professor getPro() { 35 return pro; 36 } 37 public void setPro(Professor pro) { 38 this.pro = pro; 39 } 40 } 41 class Professor implements Cloneable{ 42 private String name; 43 private int age; 44 public Professor(){} 45 public Professor(String name,int age){ 46 this.name=name; 47 this.age=age; 48 } 49 public Object clone(){ 50 Object o=null; 51 try { 52 o=super.clone(); 53 } catch (CloneNotSupportedException e) { 54 e.printStackTrace(); 55 } 56 return o; 57 } 58 public String getName() { 59 return name; 60 } 61 public void setName(String name) { 62 this.name = name; 63 } 64 public int getAge() { 65 return age; 66 } 67 public void setAge(int age) { 68 this.age = age; 69 } 70 }
public class StudentTest { public static void main(String[] args) { Professor p=new Professor("wangwu",50); Student s1=new Student("zhangsan",18,p); Student s2=(Student)s1.clone(); s2.getPro().setName("maer"); s2.getPro().setAge(40); System.out.println("name="+s1.getPro().getName() +",age="+s1.getPro().getAge()); //name=wangwu,age=50 } }
clone方法将对象复制了一份并返回给调用者。一般而言，clone（）方法满足：
①对任何的对象x，都有x.clone() !=x//克隆对象与原对象不是同一个对象
②对任何的对象x，都有x.clone().getClass()= =x.getClass()//克隆对象与原对象的类型一样
③如果对象x的equals()方法定义恰当，那么x.clone().equals(x)应该成立。
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原文地址：http://blog.csdn.net/j754379117/article/details/47026419
