Java clone()

//浅复制（浅克隆）: 浅复制仅仅复制所考虑的对象，而不复制它所引用的对象。  
//深复制（深克隆）：深复制把要复制的对象所引用的对象都复制了一遍。  
//  
//Java中对象的克隆,为了获取对象的一份拷贝，我们可以利用Object类的clone()方法。必须要遵循下面三点  
//1.在派生类中覆盖基类的clone()方法，并声明为public【Object类中的clone()方法为protected的】。  
//2.在派生类的clone()方法中，调用super.clone()。  
//3.在派生类中实现Cloneable接口。  
  public class Clone {
    public static void main(String[] args) throws Exception {
        // teacher对象将被clone出来的Student对象共享.
        Teacher teacher = new Teacher();
        teacher.setAge(40);
        teacher.setName("Teacher zhang");

        Student student1 = new Student();
        student1.setAge(20);
        student1.setName("zhangsan");
        student1.setTeacher(teacher);

        // 复制出来一个对象student2
        Student student2 = (Student) student1.clone();
        System.out.println(student2.getAge());
        System.out.println(student2.getName());

        System.out.println("~~~~~~~~~~~~~~~~~~~~~~");
        System.out.println(student1.getTeacher().getAge());
        System.out.println(student1.getTeacher().getName());

        // 修改student2的引用对象
        student2.getTeacher().setAge(50);
        student2.getTeacher().setName("Teacher Li");

        System.out.println("~~~~~~~~~~~~~~~~~~~~~~");
        System.out.println(student1.getTeacher().getAge());
        System.out.println(student1.getTeacher().getName());
    }
}

class Teacher {
    public int age;
    public String name;

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

class Student implements Cloneable {

    public int age;
    public String name;
    public Teacher teacher;

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Teacher getTeacher() {
        return teacher;
    }

    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }

    @Override
    public Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

}

95. 输出结果为：  
96. 20  
97. zhangsan  
98. ~~~~~~~~~~~~~~~~~~~~~~  
99. 40  
100. Teacher zhang  
101. ~~~~~~~~~~~~~~~~~~~~~~  
102. 50  
103. Teacher Li  

 1 public class DeepClone {
 2 
 3 
 4         public static void main(String[] args) throws Exception {
 5             // teacher对象将不被clone出来的Student对象共享.
 6             Teacher teacher = new Teacher();
 7             teacher.setAge(40);
 8             teacher.setName("Teacher zhang");
 9 
10             Student student1 = new Student();
11             student1.setAge(20);
12             student1.setName("zhangsan");
13             student1.setTeacher(teacher);
14 
15             // 复制出来一个对象student2
16             Student student2 = (Student) student1.clone();
17             System.out.println(student2.getAge());
18             System.out.println(student2.getName());
19 
20             System.out.println("~~~~~~~~~~~~~~~~~~~~~~");
21             System.out.println(student1.getTeacher().getAge());
22             System.out.println(student1.getTeacher().getName());
23 
24             // 修改student2的引用对象
25             student2.getTeacher().setAge(50);
26             student2.getTeacher().setName("Teacher Li");
27 
28             System.out.println("~~~~~~~~~~~~~~~~~~~~~~");
29             System.out.println(student1.getTeacher().getAge());
30             System.out.println(student1.getTeacher().getName());
31         }
32     }
33 
34     class Teacher implements Cloneable {
35         public int age;
36         public String name;
37 
38         public int getAge() {
39             return age;
40         }
41 
42         public void setAge(int age) {
43             this.age = age;
44         }
45 
46         public String getName() {
47             return name;
48         }
49 
50         public void setName(String name) {
51             this.name = name;
52         }
53 
54         @Override
55         public Object clone() throws CloneNotSupportedException {
56             return super.clone();
57         }
58 
59     }
60 
61     class Student implements Cloneable {
62 
63         public int age;
64         public String name;
65         public Teacher teacher;
66 
67         public int getAge() {
68             return age;
69         }
70 
71         public void setAge(int age) {
72             this.age = age;
73         }
74 
75         public String getName() {
76             return name;
77         }
78 
79         public void setName(String name) {
80             this.name = name;
81         }
82 
83         public Teacher getTeacher() {
84             return teacher;
85         }
86 
87         public void setTeacher(Teacher teacher) {
88             this.teacher = teacher;
89         }
90 
91         @Override
92         public Object clone() throws CloneNotSupportedException {
93             Student student = (Student) super.clone();
94             // 将引用的对象teacher也clone下
95             student.setTeacher((Teacher)(student.getTeacher().clone()));
96             return student;
97         }
98 
99     }

1. 输出结果为：  
2. 20  
3. zhangsan  
4. ~~~~~~~~~~~~~~~~~~~~~~  
5. 40  
6. Teacher zhang  
7. ~~~~~~~~~~~~~~~~~~~~~~  
8. 40  
9. Teacher zhang 

import java.io.ByteArrayInputStream;  
import java.io.ByteArrayOutputStream;  
import java.io.ObjectInputStream;  
import java.io.ObjectOutputStream;  
import java.io.Serializable;  
//利用序列化来做深复制  
//深clone  
public class DeepCloneTest {  
  
    public static void main(String[] args) throws Exception{  
        //teacher对象将不被clone出来的Student对象共享.  
        Teacher teacher = new Teacher();  
        teacher.setAge(40);  
        teacher.setName("Teacher zhang");  
          
        Student student1 = new Student();  
        student1.setAge(20);  
        student1.setName("zhangsan");  
        student1.setTeacher(teacher);  
          
        //复制出来一个对象student2  
        Student student2 = (Student)student1.deepCopy();
        System.out.println(student2.getAge());  
        System.out.println(student2.getName());  
          
          
        System.out.println("~~~~~~~~~~~~~~~~~~~~~~");  
        System.out.println(student1.getTeacher().getAge());  
        System.out.println(student1.getTeacher().getName());  
          
          
        //修改student2的引用对象  
        student2.getTeacher().setAge(50);  
        student2.getTeacher().setName("Teacher Li");  
          
        System.out.println("~~~~~~~~~~~~~~~~~~~~~~");  
        System.out.println(student1.getTeacher().getAge());  
        System.out.println(student1.getTeacher().getName());  
    }  
}  
  
class Teacher implements Serializable{  
      
    private static final long serialVersionUID = -8834559347461591191L;  
      
    public int age;  
    public String name;  
      
    public int getAge() {  
        return age;  
    }  
    public void setAge(int age) {  
        this.age = age;  
    }  
    public String getName() {  
        return name;  
    }  
    public void setName(String name) {  
        this.name = name;  
    }  
      
}  
  
class Student implements Serializable{  
      
    //serialVersionUID 如果你的对象序列化后存到硬盘上面后，可是后来你却更改了类的field(增加或减少或改名)，当你反序列化时，就会出现Exception的，这样就会造成不兼容性的问题。   
    //但当serialVersionUID相同时，它就会将不一样的field以type的缺省值赋值(如int型的是0,String型的是null等)，这个可以避开不兼容性的问题。所以最好给serialVersionUID赋值  
    private static final long serialVersionUID = 7991552226614088458L;  
      
    public int age ;  
    public String name;  
    public Teacher teacher;  
    public int getAge() {  
        return age;  
    }  
    public void setAge(int age) {  
        this.age = age;  
    }  
    public String getName() {  
        return name;  
    }  
    public void setName(String name) {  
        this.name = name;  
    }  
    public Teacher getTeacher() {  
        return teacher;  
    }  
    public void setTeacher(Teacher teacher) {  
        this.teacher = teacher;  
    }  
      
    public Object deepCopy() throws Exception{  
        //将该对象序列化成流,因为写在流里的是对象的一个拷贝，而原对象仍然存在于JVM里面。所以利用这个特性可以实现对象的深拷贝  
        ByteArrayOutputStream bos = new ByteArrayOutputStream();  
  
        ObjectOutputStream oos = new ObjectOutputStream(bos);  
  
        oos.writeObject(this);  
  
        //将流序列化成对象  
        ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());  
  
        ObjectInputStream ois = new ObjectInputStream(bis);  
  
        return ois.readObject();  
    }  

1. 输出结果为：  
2. 20  
3. zhangsan  
4. ~~~~~~~~~~~~~~~~~~~~~~  
5. 40  
6. Teacher zhang  
7. ~~~~~~~~~~~~~~~~~~~~~~  
8. 40  
9. Teacher zhang