摘要：為什么使用存在一個對象，已有初始值，這時候可能需要一個新的對象和相同，但是和是兩個獨立的對象，任意一個改動都不影響其中一個的值，但是的初始值由確定，這時候就是最有效也是最簡單的方法。

存在一個對象A，A已有初始值，這時候可能需要一個新的對象B和A相同，但是A和B是兩個獨立的對象，任意一個改動都不影響其中一個的值，但是B的初始值由A確定，這時候clone就是最有效也是最簡單的方法。

new操作符的本意是分配內存空間，java程序執行到new操作符時，首先去看new操作符后面的類型，知道類型才能知道需要分配多大的內存空間，分配完成，調用構造函數，填充對象，完成對象的初始化。

clone的第一步也是分配內存，java程序執行到clone這一步時，分配的內存和調用clone方法的對象相同，在根據原對象完成對新對象的初始化，一個新的對象就被創建完成。

需要克隆的對象要繼承Cloneable接口，并重寫clone()方法

定義類：

public class People1 {
    private String name;
    private Integer age;

    public People1(String name, Integer age) {
        this.name = name;
        this.age = age;
    }
}

復制測試

public class test {
    public static void main(String[] args) {
        People1 people1 = new People1("people",18);
        People1 people11 = people1;

        System.out.println(people1);
        System.out.println(people11);
        System.out.println(people1 == people11);
    }
}

結果：

證明復制對象只是指向原來的對象，people1和people11只是引用同一個對象

定義類：

public class People2 implements Cloneable{
    private String name;
    private Integer age;

    public People2(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public Integer getAge() {
        return age;
    }
    
    public void setName(String name) {
        this.name = name;
    }

    public void setAge(Integer age) {
        this.age = age;
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

測試：

public class test {
    public static void main(String[] args) {
        
        //clone
        People2 people2 = new People2("people",18);
        People2 people22 = null;
        try {
            people22 = (People2) people2.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }

        System.out.println(people2);
        System.out.println(people22);
        System.out.println(people2 == people22);
    }
}

結果：

可以看出people2和people22指向的對象并不是同一個的

定義類：
Student類：

public class Student implements Cloneable{
    private String name;
    private Integer age;
    private Teacher teacher;

    public Student(String name, Integer age,Teacher teacher) {
        this.name = name;
        this.age = age;
        this.teacher = teacher;
    }

    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 Teacher getTeacher() {
        return teacher;
    }

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

    @Override
     public String toString() {
         return "學生： name=" + name + ", age=" + age + ",指導" + teacher;
      }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

Teacher類

public class Teacher {
    private String name;
    private Integer age;

    public Teacher(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;
    }
    @Override
    public String toString() {
        return "老師：name=" + name + ", age=" + age ;
    }
}

main函數

public class test2 {
    public static void main(String[] args) {
        Teacher teacher = new Teacher("劉老師",18);
        Student student1 = new Student("小明",10,teacher);
        Student student2 = null;
        try {
            student2 = (Student) student1.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        Teacher t1 = student2.getTeacher();
        t1.setName("張老師");
        t1.setAge(30);
        student2.setName("小紅");
        student2.setAge(9);
        student2.setTeacher(t1);
        System.out.println(student1);
        System.out.println(student2);
    }
}

結果：

修改student2中的Teacher類，student1也跟著改變，而修改姓名和年齡并不會修改，由此得出才重新clone方法時不能直接super

Teacher繼承Cloneable

Student重寫clone方法

        Student newStudent = (Student) super.clone();
        newStudent.teacher = (Teacher) teacher.clone();
        return newStudent;

運行上方測試代碼，結果：

完成預想結果