java clone
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1.java里的clone分为:
A:浅复制(浅克隆): 浅复制仅仅复制所考虑的对象,而不复制它所引用的对象。
b:深复制(深克隆):深复制把要复制的对象所引用的对象都复制了一遍。
Java中对象的克隆,为了获取对象的一份拷贝,我们可以利用Object类的clone()方法。必须要遵循下面三点
1.在派生类中覆盖基类的clone()方法,并声明为public【Object类中的clone()方法为protected的】。
2.在派生类的clone()方法中,调用super.clone()。
3.在派生类中实现Cloneable接口。
Object类里的clone方法是浅复制(浅克隆)
浅复制(浅克隆)的例子如下:
A:浅复制(浅克隆): 浅复制仅仅复制所考虑的对象,而不复制它所引用的对象。
b:深复制(深克隆):深复制把要复制的对象所引用的对象都复制了一遍。
Java中对象的克隆,为了获取对象的一份拷贝,我们可以利用Object类的clone()方法。必须要遵循下面三点
1.在派生类中覆盖基类的clone()方法,并声明为public【Object类中的clone()方法为protected的】。
2.在派生类的clone()方法中,调用super.clone()。
3.在派生类中实现Cloneable接口。
Object类里的clone方法是浅复制(浅克隆)
浅复制(浅克隆)的例子如下:
package com.test; //浅复制(浅克隆): 浅复制仅仅复制所考虑的对象,而不复制它所引用的对象。 //深复制(深克隆):深复制把要复制的对象所引用的对象都复制了一遍。 // //Java中对象的克隆,为了获取对象的一份拷贝,我们可以利用Object类的clone()方法。必须要遵循下面三点 //1.在派生类中覆盖基类的clone()方法,并声明为public【Object类中的clone()方法为protected的】。 //2.在派生类的clone()方法中,调用super.clone()。 //3.在派生类中实现Cloneable接口。 //[color=red]Object类里的clone方法是浅复制(浅克隆)[/color]public class CloneTest { public static void main(String[] args) throws Exception{ //teacher对象将被clone出来的Student对象共享. Teacher teacher = new Teacher(); teacher.setAge(40); teacher.setName("Teacher zhang"); Student student1 = new Student(); student1.setAge(20); student1.setName("zhangsan"); student1.setTeacher(teacher); //复制出来一个对象student2 Student student2 = (Student)student1.clone(); System.out.println(student2.getAge()); System.out.println(student2.getName()); System.out.println("~~~~~~~~~~~~~~~~~~~~~~"); System.out.println(student1.getTeacher().getAge()); System.out.println(student1.getTeacher().getName()); //修改student2的引用对象 student2.getTeacher().setAge(50); student2.getTeacher().setName("Teacher Li"); System.out.println("~~~~~~~~~~~~~~~~~~~~~~"); System.out.println(student1.getTeacher().getAge()); System.out.println(student1.getTeacher().getName()); } } class Teacher { public int age; public 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 Student implements Cloneable{ public int age ; public String name; public 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 { return super.clone(); } }
输出结果为:
20
zhangsan
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang
~~~~~~~~~~~~~~~~~~~~~~
50
Teacher Li
2.深复制(深Clone)例子:
package com.test1;//深clonepublic class DeepCloneTest {public static void main(String[] args) throws Exception{//teacher对象将不被clone出来的Student对象共享.Teacher teacher = new Teacher();teacher.setAge(40);teacher.setName("Teacher zhang");Student student1 = new Student();student1.setAge(20);student1.setName("zhangsan");student1.setTeacher(teacher);//复制出来一个对象student2Student student2 = (Student)student1.clone();System.out.println(student2.getAge());System.out.println(student2.getName());System.out.println("~~~~~~~~~~~~~~~~~~~~~~");System.out.println(student1.getTeacher().getAge());System.out.println(student1.getTeacher().getName());//修改student2的引用对象student2.getTeacher().setAge(50);student2.getTeacher().setName("Teacher Li");System.out.println("~~~~~~~~~~~~~~~~~~~~~~");System.out.println(student1.getTeacher().getAge());System.out.println(student1.getTeacher().getName());}}class Teacher implements Cloneable{public int age;public 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;}@Overridepublic Object clone() throws CloneNotSupportedException {return super.clone();}}class Student implements Cloneable{public int age ;public String name;public 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;}@Overridepublic Object clone() throws CloneNotSupportedException {Student student = (Student)super.clone();//将引用的对象teacher也clone下student.setTeacher((Teacher)(student.getTeacher().clone()));return student;}}
输出结果为:
20
zhangsan
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang
3.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,而把对象从流中读出来的过程则叫做反序列化(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。,利用这个特性,可以做深拷贝
package com.test3;import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import java.io.Serializable;//利用序列化来做深复制//深clonepublic class DeepCloneTest {public static void main(String[] args) throws Exception{//teacher对象将不被clone出来的Student对象共享.Teacher teacher = new Teacher();teacher.setAge(40);teacher.setName("Teacher zhang");Student student1 = new Student();student1.setAge(20);student1.setName("zhangsan");student1.setTeacher(teacher);//复制出来一个对象student2Student student2 = (Student)student1.deepCopy();System.out.println(student2.getAge());System.out.println(student2.getName());System.out.println("~~~~~~~~~~~~~~~~~~~~~~");System.out.println(student1.getTeacher().getAge());System.out.println(student1.getTeacher().getName());//修改student2的引用对象student2.getTeacher().setAge(50);student2.getTeacher().setName("Teacher Li");System.out.println("~~~~~~~~~~~~~~~~~~~~~~");System.out.println(student1.getTeacher().getAge());System.out.println(student1.getTeacher().getName());}}class Teacher implements Serializable{private static final long serialVersionUID = -8834559347461591191L;public int age;public 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 Student implements Serializable{//serialVersionUID 如果你的对象序列化后存到硬盘上面后,可是后来你却更改了类的field(增加或减少或改名),当你反序列化时,就会出现Exception的,这样就会造成不兼容性的问题。 //但当serialVersionUID相同时,它就会将不一样的field以type的缺省值赋值(如int型的是0,String型的是null等),这个可以避开不兼容性的问题。所以最好给serialVersionUID赋值private static final long serialVersionUID = 7991552226614088458L;public int age ;public String name;public 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;}public Object deepCopy() throws Exception{//将该对象序列化成流,因为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。所以利用这个特性可以实现对象的深拷贝ByteArrayOutputStream bos = new ByteArrayOutputStream();ObjectOutputStream oos = new ObjectOutputStream(bos);oos.writeObject(this);//将流序列化成对象ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());ObjectInputStream ois = new ObjectInputStream(bis);return ois.readObject();}}
输出结果为:
20
zhangsan
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang
~~~~~~~~~~~~~~~~~~~~~~
40
Teacher zhang
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