java基础学习-克隆

浅复制

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。换言之，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

被复制对象的所有变量都含有与原来的对象相同的值，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。换言之，深复制把要复制的对象所引用的对象都复制了一遍（递归下去）。

Java中对象的克隆

Object的clone()方法

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。

实现：

1）为了获取对象的一份拷贝，我们可以利用Object类的clone()方法。
2）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）
3）在派生类的clone()方法中，调用super.clone()
4）在派生类中实现Cloneable接口

浅复制

public class Student implements Cloneable {private int age;private String name;private Book book;public int getAge() {return age;}public Book getBook() {return book;}public void setBook(Book book) {this.book = book;}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 {Object object = super.clone();return object;}}

public class Book {public String name;public String getName() {return name;}public void setName(String name) {this.name = name;}}

public class Test {public static void main(String[] args) throws CloneNotSupportedException {Student student1 = new Student();Book book = new Book();book.setName("english");student1.setName("zhangsan");student1.setAge(22);student1.setBook(book);Student student2 = (Student) student1.clone();System.out.println(student1.clone().equals(student1));// falseSystem.out.println(student1.clone() == student1);// falseSystem.out.println(student1.clone().getClass() == student2.getClass());// trueSystem.out.println(student2.getName());// zhangsanstudent1.setName("lisi");student1.getBook().setName("chinese");System.out.println(student2.getName());// zhangsanSystem.out.println(student2.getBook().getName());// chinese}}

深复制

方式一：利用clone方法

public class Fruit implements Cloneable {public String name;public Apple apple;public String getName() {return name;}public void setName(String name) {this.name = name;}public Apple getApple() {return apple;}public void setApple(Apple apple) {this.apple = apple;}@Overridepublic Object clone() throws CloneNotSupportedException {<strong>Fruit fruit1 = (Fruit) super.clone();fruit1.setApple((Apple) fruit1.getApple().clone());return fruit1;</strong>}}

public class Apple  implements Cloneable {public String Name = "";public String getName() {return Name;}public void setName(String name) {Name = name;}@Overridepublic Object clone() throws CloneNotSupportedException {<strong>return super.clone();</strong>}}

public class Test {public static void main(String[] args) throws Exception {Fruit fruit1 = new Fruit();Apple apple = new Apple();fruit1.setName("apple");apple.setName("fusi");fruit1.setApple(apple);Fruit fruit2 = (Fruit) fruit1.clone();System.out.println(fruit1.clone().equals(fruit1));// falseSystem.out.println(fruit1.clone() == fruit1);// falseSystem.out.println(fruit1.clone().getClass() == fruit2.getClass());// trueSystem.out.println(fruit2.getName());// applefruit1.setName("banana");fruit1.getApple().setName("shandong");System.out.println(fruit2.getName());// appleSystem.out.println(fruit2.getApple().getName());// fusi}}

方式二：序列化方式

public class People  implements Serializable {public String name;public Girl girl;public String getName() {return name;}public void setName(String name) {this.name = name;}public Girl getGirl() {return girl;}public void setGirl(Girl girl) {this.girl = girl;}public Object deepCopy() throws Exception{ByteArrayOutputStream bos = new ByteArrayOutputStream();ObjectOutputStream oos = new ObjectOutputStream(bos);oos.writeObject(this);ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());ObjectInputStream ois = new ObjectInputStream(bis);return ois.readObject();}}

public class Girl  implements Serializable {public String name;public String getName() {return name;}public void setName(String name) {this.name = name;}}

public class Test {public static void main(String[] args) throws Exception {People people1 = new People();Girl girl = new Girl();people1.setName("zhangsan");girl.setName("meimei");people1.setGirl(girl);People people2 = (People) people1.deepCopy();System.out.println(people1.deepCopy().equals(people1));// falseSystem.out.println(people1.deepCopy() == people1);// falseSystem.out.println(people1.deepCopy().getClass() == people2.getClass());// trueSystem.out.println(people2.getName());// zhangsanpeople1.setName("lisi");people1.getGirl().setName("lili");System.out.println(people2.getName());// zhangsanSystem.out.println(people2.getGirl().getName());// meimei}}