当我克隆父 Object 时，它会修改原始父的子对象

Question

I am trying to clone a Object which has Arrays and then each element in that Array also has Arrays of a different object. Object Structure is as below:

School - SchClass[] - Students[]

I have a helper class which has the below line of code to clone the School object.

Helper.java:

schoolClone = (School) originalSchool.clone();

School.java

public object School(){
    School school = null;
    try{
        school = (School) super.clone();
    }
    catch (CloneNotSupportedException e) {
        school = new School();
    }
    school.schClasses = (SchClass[]) this.schClasses.clone();    
    return school;
}

SchClass.java

public object SchClass(){
    SchClass schClass = new SchClass();
    schClass.students = (Student[]) this.students.clone();
    return schClass;
}

Student.java

public object Student(){
    Student student = null;
    try{
        student = (Student) super.clone();
    }catch (CloneNotSupportedException e) {
        student = new Student(this.getName(), this.getAge(), this.getGrade());
    }
    return student;
}

If I remove a student from the schoolClone object, it gets removed from the originalSchool object too (this is my problem)** however if I removed any schClass object from the schoolClone object, the originalSchool object remains as it is and the data is modified only on the cloned object.

Is there a way I can remove a student from the schoolClone object but it does not affect my originalSchool object.

Any help is appreciated.

Answer 1

1. When you clone an array, it only clones the array, not the elements in the array,
2. If you make a copy of an object that contains "children" objects, and these "children" objects have a field that references the "parent", the value of that field must be updated so that it references the clone of the parent.

I personally avoid clone like the plague. I rather use copy constructors.

Answer 2

I think you are using shallow cloning instead of deep cloning. you have to use deep cloning and override the clone method according to your requirements.