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。

Teacher?teacher?=?new?Teacher(Taylor,26);
Teacher?otherteacher?=?teacher;
System.out.println(teacher);
System.out.println(otherteacher);

输出结果：

blog.Teacher@355da254
blog.Teacher@355da254

结果分析：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(“Taylor”,26)。这就叫做引用拷贝。往期：一百期面试题汇总

（2）、对象拷贝

创建对象本身的一个副本。

Teacher?teacher?=?new?Teacher(Swift,26);?
Teacher?otherteacher?=?(Teacher)teacher.clone();?
System.out.println(teacher);
System.out.println(otherteacher);

输出结果：

blog.Teacher@355da254
blog.Teacher@4dc63996

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。往期：100期面试题汇总

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

package?com.test;

public?class?ShallowCopy?{
????public?static?void?main(String[]?args)?throws?CloneNotSupportedException?{
????????Teacher?teacher?=?new?Teacher();
????????teacher.setName(riemann);
????????teacher.setAge(27);

????????Student2?student1?=?new?Student2();
????????student1.setName(edgar);
????????student1.setAge(18);
????????student1.setTeacher(teacher);

????????Student2?student2?=?(Student2)?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(Games);
????????System.out.println(student1.getTeacher().getName());
????????System.out.println(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?Student2?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;
????}
}

输出结果：

拷贝后
edgar
18
riemann
27
修改老师的信息后-------------
Games
Games

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。

往期：100期面试题汇总

（2）、深拷贝实例

package?com.test;

public?class?DeepCopy?{
????public?static?void?main(String[]?args)?throws?CloneNotSupportedException?{
????????Teacher2?teacher?=?new?Teacher2();
????????teacher.setName(riemann);
????????teacher.setAge(27);

????????Student3?student1?=?new?Student3();
????????student1.setName(edgar);
????????student1.setAge(18);
????????student1.setTeacher(teacher);

????????Student3?student2?=?(Student3)?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(Games);
????????System.out.println(student1.getTeacher().getName());
????????System.out.println(student2.getTeacher().getName());
????}
}

class?Teacher2?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?Student3?implements?Cloneable?{
????private?String?name;
????private?int?age;
????private?Teacher2?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?Teacher2?getTeacher()?{
????????return?teacher;
????}

????public?void?setTeacher(Teacher2?teacher)?{
????????this.teacher?=?teacher;
????}

????public?Object?clone()?throws?CloneNotSupportedException?{
????????//?浅复制时：
????????//?Object?object?=?super.clone();
????????//?return?object;

????????//?改为深复制：
????????Student3?student?=?(Student3)?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((Teacher2)?student.getTeacher().clone());
????????return?student;

????}
}

输出结果：

拷贝后
edgar
18
riemann
27
修改老师的信息后-------------
Games
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。

作者：riemann
blog.csdn.net/riemann_/article/details/87217229

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