一、拷贝的引入
（1）、引用拷贝
创建一个指向对象的引用变量的拷贝。
public class QuoteCopy {
public static void main(String[] args) {
Teacher teacher = new Teacher("riemann", 28);
Teacher otherTeacher = teacher;
System.out.println(teacher);
System.out.println(otherTeacher);
}
}
class Teacher {
private String name;
private int age;
public Teacher(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
com.test.Teacher@28a418fc com.test.Teacher@28a418fc
由输出结果可以看出，它们的地址值是相同的，那么它们肯定是同一个对象。teacher和otherTeacher的只是引用而已，他们都指向了一个相同的对象Teacher(“riemann”,28)。 这就叫做引用拷贝。
（2）、对象拷贝
创建对象本身的一个副本。
public class ObjectCopy {
public static void main(String[] args) throws CloneNotSupportedException {
Teacher teacher = new Teacher("riemann", 28);
Teacher otherTeacher = (Teacher) teacher.clone();
System.out.println(teacher);
System.out.println(otherTeacher);
}
}
class Teacher implements Cloneable {
private String name;
private int age;
public Teacher(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Object clone() throws CloneNotSupportedException {
Object object = super.clone();
return object;
}
}
com.test.Teacher@28a418fc com.test.Teacher@5305068a
结果分析：由输出结果可以看出，它们的地址是不同的，也就是说创建了新的对象， 而不是把原对象的地址赋给了一个新的引用变量,这就叫做对象拷贝。
注：深拷贝和浅拷贝都是对象拷贝
二、浅拷贝
（1）、定义
被复制对象的所有变量都含有与原来的对象相同的值，而所有的对其他对象的引用仍然指向原来的对象。即对象的浅拷贝会对“主”对象进行拷贝，但不会复制主对象里面的对象。”里面的对象“会在原来的对象和它的副本之间共享。
简而言之，浅拷贝仅仅复制所考虑的对象，而不复制它所引用的对象。
（2）、浅拷贝实例
public class ShallowCopy {
public static void main(String[] args) throws CloneNotSupportedException {
Teacher teacher = new Teacher();
teacher.setName("riemann");
teacher.setAge(28);
Student student1 = new Student();
student1.setName("edgar");
student1.setAge(18);
student1.setTeacher(teacher);
Student student2 = (Student) student1.clone();
System.out.println("-------------拷贝后-------------");
System.out.println(student2.getName());
System.out.println(student2.getAge());
System.out.println(student2.getTeacher().getName());
System.out.println(student2.getTeacher().getAge());
System.out.println("-------------修改老师的信息后-------------");
// 修改老师的信息
teacher.setName("jack");
System.out.println("student1的teacher为： " + student1.getTeacher().getName());
System.out.println("student2的teacher为： " + student2.getTeacher().getName());
}
}
class Teacher implements Cloneable {
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
class Student implements Cloneable {
private String name;
private int age;
private Teacher teacher;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Teacher getTeacher() {
return teacher;
}
public void setTeacher(Teacher teacher) {
this.teacher = teacher;
}
public Object clone() throws CloneNotSupportedException {
Object object = super.clone();
return object;
}
}
-------------拷贝后------------- edgar 18 riemann 28 -------------修改老师的信息后------------- student1的teacher为： jack student2的teacher为： jack
结果分析： 两个引用student1和student2指向不同的两个对象，但是两个引用student1和student2中的两个teacher引用指向的是同一个对象，所以说明是浅拷贝。
三、深拷贝
（1）、定义
深拷贝是一个整个独立的对象拷贝，深拷贝会拷贝所有的属性,并拷贝属性指向的动态分配的内存。当对象和它所引用的对象一起拷贝时即发生深拷贝。深拷贝相比于浅拷贝速度较慢并且花销较大。
简而言之，深拷贝把要复制的对象所引用的对象都复制了一遍。
（2）、深拷贝实例
public class DeepCopy {
public static void main(String[] args) throws CloneNotSupportedException {
Teacher teacher = new Teacher();
teacher.setName("riemann");
teacher.setAge(28);
Student student1 = new Student();
student1.setName("edgar");
student1.setAge(18);
student1.setTeacher(teacher);
Student student2 = (Student) student1.clone();
System.out.println("-------------拷贝后-------------");
System.out.println(student2.getName());
System.out.println(student2.getAge());
System.out.println(student2.getTeacher().getName());
System.out.println(student2.getTeacher().getAge());
System.out.println("-------------修改老师的信息后-------------");
// 修改老师的信息
teacher.setName("jack");
System.out.println("student1的teacher为： " + student1.getTeacher().getName());
System.out.println("student2的teacher为： " + student2.getTeacher().getName());
}
}
class Teacher implements Cloneable {
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
}
class Student implements Cloneable {
private String name;
private int age;
private Teacher teacher;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Teacher getTeacher() {
return teacher;
}
public void setTeacher(Teacher teacher) {
this.teacher = teacher;
}
public Object clone() throws CloneNotSupportedException {
// 浅复制时：
// Object object = super.clone();
// return object;
// 改为深复制：
Student student = (Student) super.clone();
// 本来是浅复制，现在将Teacher对象复制一份并重新set进来
student.setTeacher((Teacher) student.getTeacher().clone());
return student;
}
}
-------------拷贝后------------- edgar 18 riemann 28 -------------修改老师的信息后------------- student1的teacher为： jack student2的teacher为： riemann
结果分析：
两个引用student1和student2指向不同的两个对象，两个引用student1和student2中的两个teacher引用指向的是两个对象，但对teacher对象的修改只能影响student1对象,所以说是深拷贝。
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版权声明：本文为CSDN博主「老周聊架构」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/riemann_/article/details/87217229