JAVA深复制(深克隆)与浅复制(浅克隆)

浅复制与深复制概念

1.浅复制（浅克隆）

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。

2.深复制（深克隆）
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。

Java的clone()方法

1.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

2.对任何的对象x，都有x.clone() !=x  因为克隆对象与原对象不是同一个对象

3.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

4.如果对象x的equals()方法定义恰当，那么x.clone().equals(x)应该成立

Java中对象的克隆

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

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

实例代码:

public class User implements Cloneable {

    private String name;
    private Integer age;

    
    public User(String name, Integer age) {
        super();
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public Object clone() {
        Object o = null;
        try {
            //Object中的clone()识别出你要复制的是哪一个对象
            o = (User) super.clone();       
        } catch (CloneNotSupportedException e) {
            System.out.println(e.toString());
        }
        return o;
    }
    
    
}


public class Demo06 {

    public static void main(String[] args) {
        
        User u = new User("xiaoming",20);
        User u2 = (User)u.clone();
        u2.setName("lisi");
        u2.setAge(30);
        System.out.println("name="+u.getName()+","+"age="+u.getAge());
        System.out.println("name="+u2.getName()+","+"age="+u2.getAge());
    }
}72 
输出结果：
name=xiaoming,age=20
name=lisi,age=30

说明：
为什么我们在派生类中覆盖Object的clone()方法时，一定要调用super.clone()呢？在运行时刻，Object中的clone()识别出你要复制的是哪一个对象，然后为此对象分配空间，并进行对象的复制，将原始对象的内容一一复制到新对象的存储空间中。

 浅克隆

public class Professor {

    private String name;
    private Integer age;
    
    public Professor(String name, Integer age) {
        super();
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
}

public class Student implements Cloneable {

    private String name;
    private Integer age;
    
    //引用
    private Professor professor;

    public Student(String name, Integer age, Professor professor) {
        super();
        this.name = name;
        this.age = age;
        this.professor = professor;
    }

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Professor getProfessor() {
        return professor;
    }

    public void setProfessor(Professor professor) {
        this.professor = professor;
    }
    
    @Override
    public Object clone() {
        Object o = null;
        try {
            //Object中的clone()识别出你要复制的是哪一个对象
            o = (Student) super.clone();       
        } catch (CloneNotSupportedException e) {
            System.out.println(e.toString());
        }
        return o;
    }
}

测试
public class Demo07 {

    public static void main(String[] args) {
        
        Professor p = new Professor("wangwu", 50);
        Student s1 = new Student("xiaoming",20,p);
        Student s2 = (Student) s1.clone();
        s2.getProfessor().setName("wangxiaowu");
        s2.getProfessor().setAge(30);
        System.out.println("name="+s1.getProfessor().getName()+","+"age="+s1.getProfessor().getAge());
        System.out.println("name="+s2.getProfessor().getName()+","+"age="+s2.getProfessor().getAge());
    }

}

输出结果：
name=wangxiaowu,age=30
name=wangxiaowu,age=30

深克隆

public class Professor implements Cloneable {

    private String name;
    private Integer age;

    public Professor(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Object clone() {

        Object o = null;
        try {
            o = super.clone();
        } catch (CloneNotSupportedException e) {
            System.out.println(e.toString());
        }
        return o;
    }

}

Student类:
public class Student implements Cloneable {

    private String name;
    private Integer age;
    private Professor professor;

    public Student(String name, Integer age, Professor professor) {
        this.name = name;
        this.age = age;
        this.professor = professor;
    }

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Professor getProfessor() {
        return professor;
    }

    public void setProfessor(Professor professor) {
        this.professor = professor;
    }

    public Object clone() {

        Student o = null;
        try {
            o = (Student) super.clone();
        } catch (CloneNotSupportedException e) {
            System.out.println(e.toString());
        }
        o.professor = (Professor) professor.clone();
        return o;
    }
}

测试：
public class Demo01 {

    public static void main(String[] args) {

        Professor p = new Professor("wangwu", 50);
        Student s1 = new Student("xiaoming", 20, p);
        Student s2 = (Student) s1.clone();
        s2.getProfessor().setName("xiaowangwu");
        s2.getProfessor().setAge(40);
        System.out.println("name=" + s1.getProfessor().getName()
                + "," + "age=" + s1.getProfessor().getAge());
        System.out.println("name=" + s2.getProfessor().getName()
                + "," + "age=" + s2.getProfessor().getAge());
    }
}

输出结果：

name=wangwu,age=50
name=xiaowangwu,age=40