Java浅复制与深复制

Java浅复制与深复制

• 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。
• 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中对象的克隆,为了获取对象的一份拷贝，我们可以利用Object类的clone()方法。必须要遵循下面三点
1.在派生类中覆盖基类的clone()方法，并声明为public【Object类中的clone()方法为protected的】。
2.在派生类的clone()方法中，调用super.clone()。
3.在派生类中实现Cloneable接口。
Object类里的clone方法是浅复制（浅克隆）

浅复制：

public static void main(String[] args) throws CloneNotSupportedException {        Teacher teacher = new Teacher();        teacher.setAge(40);        teacher.setName("Teacher Zhang");        Student student1 = new Student();        student1.setAge(20);        student1.setName("zhangsan");        student1.setTeacher(teacher);        Student student2 = (Student) student1.clone();        System.out.println(student2.getAge());        System.out.println(student2.getName());        System.out.println(student2.getTeacher().getAge());        System.out.println(student2.getTeacher().getName());        System.out.println("~~~~~~~~~~~~~~~~~~~~~~~");        System.out.println(student1.getTeacher().getAge());        System.out.println(student1.getTeacher().getName());        student2.setAge(18);        student2.getTeacher().setAge(50);// 浅复制针对对象的引用没有重新开辟新的空间        student2.getTeacher().setName("Teacher Li"); // 改变值后相应的都改变        System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~");        System.out.println(student1.getAge());        System.out.println(student1.getTeacher().getAge());        System.out.println(student1.getTeacher().getName());    }}class Teacher {    private int age;    private String name;    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}class Student implements Cloneable {    private int age;    private String name;    private Teacher teacher;    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Teacher getTeacher() {        return teacher;    }    public void setTeacher(Teacher teacher) {        this.teacher = teacher;    }    public Object clone() throws CloneNotSupportedException {        return super.clone();    }

输出：

20zhangsan40Teacher Zhang~~~~~~~~~~~~~~~~~~~~~~~40Teacher Zhang~~~~~~~~~~~~~~~~~~~~~~~~2050Teacher Li

深复制：

public static void main(String[] args) throws CloneNotSupportedException {        Teacher teacher = new Teacher();        teacher.setAge(40);        teacher.setName("Teacher Zhang");        Student student1 = new Student();        student1.setAge(20);        student1.setName("zhangsan");        student1.setTeacher(teacher);        Student student2 = (Student) student1.clone();        System.out.println(student2.getAge());        System.out.println(student2.getName());        System.out.println(student2.getTeacher().getAge());        System.out.println(student2.getTeacher().getName());        System.out.println("~~~~~~~~~~~~~~~~~~~~~~~");        System.out.println(student1.getTeacher().getAge());        System.out.println(student1.getTeacher().getName());        student2.setAge(18);        student2.getTeacher().setAge(50);        student2.getTeacher().setName("Teacher Li");         System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~");        System.out.println(student1.getAge());        System.out.println(student1.getTeacher().getAge());        System.out.println(student1.getTeacher().getName());    }}class Teacher implements Cloneable {    private int age;    private String name;    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Object clone() throws CloneNotSupportedException {        return super.clone();    }}class Student implements Cloneable {    private int age;    private String name;    private Teacher teacher;    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Teacher getTeacher() {        return teacher;    }    public void setTeacher(Teacher teacher) {        this.teacher = teacher;    }    public Object clone() throws CloneNotSupportedException {        Student student = (Student) super.clone();        student.setTeacher((Teacher) (student.getTeacher().clone()));        return student;    }

输出：

20zhangsan40Teacher Zhang~~~~~~~~~~~~~~~~~~~~~~~40Teacher Zhang~~~~~~~~~~~~~~~~~~~~~~~~2040Teacher Zhang