深拷贝(deep clone)与浅拷贝(shallow clone)
作者:互联网
一、浅复制和深复制概念
浅复制(浅克隆): 被复制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,而不是复制它所引用的对象。
深复制(深克隆): 被复制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, 而不再试原有的那些被引用的对象。换言之,深复制把复制的对象所应用的对象都复制了一遍。
二、Java的Clone()方法 【定义在Object类中】
clone方法将对象复制一份并返回给调用者。
一般而言,clone() 方法满足:
1、对任何对象x,都有x.clone() != x
克隆对象与原对象不是一个对象
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
二、浅复制Demo
public class CloneTest1 { public static void main(String[] args) throws CloneNotSupportedException { Student student = new Student(); student.setAge(20); student.setName("Larry"); Student student2 = (Student)student.clone(); System.out.println(student2.getAge()); System.out.println(student2.getName()); System.out.println("-----------------------"); student2.setName("Nick"); System.out.println(student.getName()); System.out.println(student2.getName()); } } class Student 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 public Object clone() throws CloneNotSupportedException { Object object = super.clone(); return object; } }
打印结果
20
zhangsan
-----------------------
zhangsan
Lisi
student2.setName("Nick"); 执行后,student2的name赋予新的值,指向新的空间。如下图
三、深复制
以下代码还是浅复制
public class CloneTest2 { public static void main(String[] args) throws CloneNotSupportedException { 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.getAge()); System.out.println(s2.getName()); teacher.setName("Teacher Li"); System.out.println(s2.getTeacher().getAge()); System.out.println(s2.getTeacher().getName()); } } class Teacher { 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 { Object object = super.clone(); return object; } }
修改成深复制
Teacher也实现Clone方法
然后改写Student的Clone方法
clone Student的时候,修改Teacher。
修改后的完整代码:
public class CloneTest2 { public static void main(String[] args) throws CloneNotSupportedException { 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.getAge()); System.out.println(s2.getName()); teacher.setName("Teacher Li"); System.out.println(s2.getTeacher().getAge()); System.out.println(s2.getTeacher().getName()); } } 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 public Object clone() throws CloneNotSupportedException { 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; } }
五、利用序列化来做深复制
把对象写到流里的过程是序列化(Serilization)过程,而把对象从流中读取出来的过程则叫饭序列化(Deserialization)过程。应当指出的是,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
使用Clone方法实现深复制存在的缺点: 存在多个引用的成员变量,将做多次处理。
如上图做了一次处理,如果有多个应用,将做多次处理。
标签:name,Teacher,age,shallow,public,teacher,拷贝,clone 来源: https://www.cnblogs.com/linlf03/p/10850391.html