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;
	}

	@Override
	public 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));// false
		System.out.println(student1.clone() == student1);// false
		System.out.println(student1.clone().getClass() == student2.getClass());// true
		System.out.println(student2.getName());// zhangsan
		student1.setName("lisi");
		student1.getBook().setName("chinese");
		System.out.println(student2.getName());// zhangsan
		System.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;
	}

	@Override
	public 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;
	}

	@Override
	public 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));// false
		System.out.println(fruit1.clone() == fruit1);// false
		System.out.println(fruit1.clone().getClass() == fruit2.getClass());// true
		System.out.println(fruit2.getName());// apple
		fruit1.setName("banana");
		fruit1.getApple().setName("shandong");
		System.out.println(fruit2.getName());// apple
		System.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));// false
		System.out.println(people1.deepCopy() == people1);// false
		System.out.println(people1.deepCopy().getClass() == people2.getClass());// true
		System.out.println(people2.getName());// zhangsan
		people1.setName("lisi");
		people1.getGirl().setName("lili");
		System.out.println(people2.getName());// zhangsan
		System.out.println(people2.getGirl().getName());// meimei
	}
}