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;

}
}