java(30) - 对象浅克隆和深克隆

一.浅克隆和深克隆的概念：

       1).浅克隆：又称为浅复制，被复制的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。换而言之，浅复制仅仅复制所考虑的对象，而不复制它所引用的对象。

       2).深克隆：又称为深复制，被复制的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。换而言之，深复制就是把要复制的对象所引用的对象都复制了一遍。

二.浅克隆实现：

<pre class="java" name="code"><strong><span style="font-size:18px;">public class Main {

	public static void main(String[] args) throws Exception {
		Student student1 = new Student();
        student1.setName("张三");
        student1.setSex("男");
        student1.setNumber(10);
        
		Student student2 = (Student)student1.clone();
		
		System.out.println(student2.getName() +" "+ student2.getNumber() +" "+ student2.getSex());
        
		student1.setName("李四");
		System.out.println(student1.getName());
		System.out.println(student2.getName());
		System.out.println(student1 == student2);
		System.out.println(student1.getClass() == student2.getClass());
	}
}

class Student implements Cloneable{
	int number;
	String name;
	String sex;

	public int getNumber() {
		return number;
	}

	public void setNumber(int number) {
		this.number = number;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	@Override
	protected Object clone() throws CloneNotSupportedException {
		Object obj = super.clone(); 
		return obj;
	}
}</span></strong>

打印：

张三 10 男
李四
张三
false
true

Object的clone方法就是浅克隆，clone()方法满足（1）.对任何对象obj，都有obj.clone()!=obj，克隆的对象与原对象不是一个对象。

三.深克隆实现（这种方式较为麻烦，一般用序列化实现）：

public class Main {

	public static void main(String[] args) throws Exception {
	
		Teacher teacher = new Teacher();
		teacher.setName("李四");
		teacher.setNumber(20);
		
		Student stu = new Student();
		stu.setName("张三");
		stu.setNumber(10);
		stu.setSex("男");
		stu.setTeacher(teacher);
		
		Student stu2 = (Student)stu.clone();
		
		System.out.println(stu2.getTeacher().getName());
		
		teacher.setName("王五");
		//如果是浅克隆则打印王五，因为teacher引用没变，变得时候teacher中的name属性
		System.out.println(stu2.getTeacher().getName());
		
		
	}
}
class Teacher implements Cloneable{
	int number;
	String name;
	public int getNumber() {
		return number;
	}
	public void setNumber(int number) {
		this.number = number;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@Override
	protected Object clone() throws CloneNotSupportedException {
		
		return super.clone();
	}
}
class Student implements Cloneable{
	int number;
	String name;
	String sex;
    Teacher  teacher;
    
	public Teacher getTeacher() {
		return teacher;
	}

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

	public int getNumber() {
		return number;
	}

	public void setNumber(int number) {
		this.number = number;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	@Override
	protected Object clone() throws CloneNotSupportedException {
      
		Student student = (Student)super.clone();
		
		student.setTeacher((Teacher)student.getTeacher().clone());
		return student;
	}
}

打印：

李四
李四