深拷贝 & 浅拷贝

浅拷贝:

class Professor {
    String name;
    int age;

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

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

class Student implements Cloneable {
    String name;
    int age;
    Professor p;

    public Student(String name, int age, Professor p) {
        this.name = name;
        this.age = age;
        this.p = p;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Student s = (Student) super.clone();
//        s.p = (Professor) p.clone();
        return s;
    }
}

public class Main {
    public static void main(String[] args) throws CloneNotSupportedException {
        Professor p = new Professor("教授1", 50);
        Student s1 = new Student("学生1", 18, p);
        Student s2 = (Student) s1.clone();

        s2.p.name = "教授2";
        s2.p.age = 30;
        s2.name = "学生2";
        s2.age = 25;
        System.out.println(s1.name + " " + s1.age + " " + s1.p.name + " " + s1.p.age);
    }
}

结果: 学生1 18 教授2 30

深拷贝：

class Professor implements Cloneable {
    String name;
    int age;

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

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

class Student implements Cloneable {
    String name;
    int age;
    Professor p;

    public Student(String name, int age, Professor p) {
        this.name = name;
        this.age = age;
        this.p = p;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Student s = (Student) super.clone();
        s.p = (Professor) p.clone();
        return s;
    }
}

public class Main {
    public static void main(String[] args) throws CloneNotSupportedException {
        Professor p = new Professor("教授1", 50);
        Student s1 = new Student("学生1", 18, p);
        Student s2 = (Student) s1.clone();

        s2.p.name = "教授2";
        s2.p.age = 30;
        s2.name = "学生2";
        s2.age = 25;
        System.out.println(s1.name + " " + s1.age + " " + s1.p.name + " " + s1.p.age);
    }
}

结果: 学生1 18 教授1 50

序列化形式深拷贝:

class Professor implements Serializable {
    private static final long serialVersionUID = 1286716519490813020L;
    String name;
    int age;

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

class Student implements Serializable {
    private static final long serialVersionUID = -547004870369127943L;
    String name;
    int age;
    Professor p;

    public Student(String name, int age, Professor p) {
        this.name = name;
        this.age = age;
        this.p = p;
    }

    public Object deepClone() throws IOException, ClassNotFoundException {
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
        objectOutputStream.writeObject(this);

        ObjectInputStream objectInputStream = new ObjectInputStream(new ByteArrayInputStream(byteArrayOutputStream.toByteArray()));
        return objectInputStream.readObject();
    }
}

public class Main {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        Professor p = new Professor("教授1", 50);
        Student s1 = new Student("学生1", 18, p);
        Student s2 = (Student) s1.deepClone();

        s2.p.name = "教授2";
        s2.p.age = 30;
        s2.name = "学生2";
        s2.age = 25;
        System.out.println(s1.name + " " + s1.age + " " + s1.p.name + " " + s1.p.age);
    }
}

结果: 学生1 18 教授1 50