Object类clone方法

今天药忘吃喽~ 2023-06-05 08:46 25阅读 0赞

Object中clone()方法是protected的，是浅拷贝，要使用clone方法，要重写它，只有实现了implements Cloneable才可以调用该方法，否则会抛出CloneNotSupportedException异常。

@Override
        public Object clone(){
            Object o = null;
            try {
                o = super.clone();
            }catch (CloneNotSupportedException e){
                e.printStackTrace();
            }
    //        Person p = (Person) o;
    //        p.book = (Book)p.getBook().clone();              //放开这两段即为深拷贝的用法
            return o;
        }

在我们需要复制对象的时候常用的三种方式

public static void main(String[] args){
        
        Book b = new Book("java");
        Person p = new Person("wt",b);
        Person p1 = new Person(p);
        Person p2 = (Person) p.clone();
        b.setBookName("js");
        p.setName("zjj");
        System.out.println("P:"+p);
        System.out.println("P1:"+p1);
        System.out.println("P2:"+p2);
    }

当clone使用浅拷贝（即不放开那两段）时，只拷贝对象不包含对对象引用的对象的拷贝：

P:{name:zjj, book:{bookName:js}}            
    P1:{name:wt, book:{bookName:js}}      //不论是p1还是p2，基本类型的数值是直接拷贝值的，但是引用类型的对象却是拷贝地址的
    P2:{name:wt, book:{bookName:js}}      //这样一旦p的原始值引用的对象改变，浅拷贝后的对象也会随之变化

当clone使用深拷贝（即放开那两段）时：

P2:{name:wt, book:{bookName:java}}      //深拷贝时，连对象中的对象都进行的是值拷贝，所以原始值的引用对象改变不会影响它

完整源代码：

person类

public class Person implements Cloneable {
        private String name;
        private Book book;
    
        public Person(String name, Book book) {
            this.name = name;
            this.book = book;
        }
    
        public Person(Person p) {
            this.name = p.name;
            this.book = p.book;
        }
    
        @Override
        public Object clone(){
            Object o = null;
            try {
                o = super.clone();
            }catch (CloneNotSupportedException e){
                e.printStackTrace();
            }
            Person p = (Person) o;
            p.book = (Book)p.getBook().clone();
            return o;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public Book getBook() {
            return book;
        }
    
        public void setBook(Book book) {
            this.book = book;
        }
    
        @Override
        public String toString() {
            return "{name:" + name + ", book:" + book + "}";
        }
    }

book类

public class Book implements Cloneable{
        private String bookName;
        public Book(String bookName) {
            this.bookName = bookName;
        }
    
        public String getBookName() {
            return bookName;
        }
    
        public void setBookName(String bookName) {
            this.bookName = bookName;
        }
    
        @Override
        public String toString() {
            return "{bookName:" + bookName + "}";
        }
    
        @Override
        public Object clone(){
            Object o = null;
            try {
                o = super.clone();
            }catch (CloneNotSupportedException e){
                e.printStackTrace();
            }
            return o;
        }
    }

clone测试类

public class CloneTest {
    
        public static void main(String[] args){
            Book b = new Book("java");
            Person p = new Person("wt",b);
            Person p1 = new Person(p);
            Person p2 = (Person) p.clone();
            b.setBookName("js");
            p.setName("zjj");
            System.out.println("P:"+p);
            System.out.println("P1:"+p1);
            System.out.println("P2:"+p2);
        }
    }

转载于:https://www.cnblogs.com/sycamore0802/p/11247877.html