java语言——对象的深复制（deep clone）与浅复制（shallow clone）

-浅复制（浅克隆）：被复制的对象的所有变量都含有与原来对象相同的值，而所有的对其他对象的引用仍然指向原来的对象。换言之，浅复制仅仅复制所考虑的对象。而不复制他所引用的对象。

-深复制（深克隆）：被复制的对象的所有变量都含有与原来对象相同的值，除去那些引用其他对象的变量。那些引用其他对象的变量将指向被复制过的新对象，而不再是原有的那些被引用的对象。换而言之，深复制把要复制的对象所引用的对象都复制了一遍。

Java的clone()方法【定义在Object类中】

-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()

克隆对象与原来对象的类型一样

-（3）如果对象x的equals()方法定义恰当，那么x.clone().equals(x)应该成立。

浅复制：

package clone;public class CloneTest2 {     public static void main(String[] args) throws Throwable {        Teacher teacher = new Teacher();                teacher.setAge(40);        teacher.setName("Teacher zhang");                Student2 s1 = new Student2();                s1.setAge(20);        s1.setName("zhangsan");        s1.setTeacher(teacher);                Student2 s2 = (Student2)s1.clone();        System.out.println(s2.getTeacher().getName());        System.out.println(s2.getTeacher().getAge());                System.out.println("----------------------------------------");        teacher.setName("Teacher li");        System.out.println(s2.getTeacher().getName());        System.out.println(s2.getTeacher().getAge());    }}class Teacher implements Cloneable{    private int age;        private 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 Student2 implements Cloneable{    private int age;        private String name;        private 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 {        // TODO Auto-generated method stub        return super.clone();    }}

 深复制：

package clone;public class CloneTest2 {     public static void main(String[] args) throws Throwable {        Teacher teacher = new Teacher();                teacher.setAge(40);        teacher.setName("Teacher zhang");                Student2 s1 = new Student2();                s1.setAge(20);        s1.setName("zhangsan");        s1.setTeacher(teacher);                Student2 s2 = (Student2)s1.clone();        System.out.println(s2.getTeacher().getName());        System.out.println(s2.getTeacher().getAge());                System.out.println("----------------------------------------");        teacher.setName("Teacher li");        System.out.println(s2.getTeacher().getName());        System.out.println(s2.getTeacher().getAge());    }}class Teacher implements Cloneable{    private int age;        private 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;    }    @Override    protected Object clone() throws CloneNotSupportedException {        // TODO Auto-generated method stub        return super.clone();    }}class Student2 implements Cloneable{    private int age;        private String name;        private 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 {        Student2 student2 = (Student2)super.clone();                student2.setTeacher((Teacher)student2.getTeacher().clone());                return student2;            }}

package clone;public class CloneTest2 {     public static void main(String[] args) throws Throwable {        Teacher teacher = new Teacher();                teacher.setAge(40);        teacher.setName("Teacher zhang");                Student2 s1 = new Student2();                s1.setAge(20);        s1.setName("zhangsan");        s1.setTeacher(teacher);                Student2 s2 = (Student2)s1.clone();        System.out.println(s2.getTeacher().getName());        System.out.println(s2.getTeacher().getAge());                System.out.println("----------------------------------------");        teacher.setName("Teacher li");        System.out.println(s2.getTeacher().getName());        System.out.println(s2.getTeacher().getAge());    }}class Teacher implements Cloneable{    private int age;        private 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;    }    @Override    protected Object clone() throws CloneNotSupportedException {        // TODO Auto-generated method stub        return super.clone();    }}class Student2 implements Cloneable{    private int age;        private String name;        private 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 {        Student2 student2 = (Student2)super.clone();                student2.setTeacher((Teacher)student2.getTeacher().clone());                return student2;            }}