java浅拷贝和深拷贝

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这就是java浅拷贝，2个对象的引用地址一样，任意一个对象对字段的修改都会引起另一个对象数据的修改

Professor p = new Professor("wangwu", 50);    Professor p2=p;    p2.name="zhangmin";    System.out.println(p.getName());    System.out.println(p2.getName());

上面显然是不合适的，要解决这个问题就需要深拷贝的概念。

深拷贝是真正开辟一个属于自己的内存空间，而不是空间地址的引用。

有笔者以为只要 Professor实现了Cloneable接口，就可以实现深拷贝，是错误的概念，如下：

public class Professor implements Cloneable {    String name;    int age;     Professor(String name, int age) {        this.name = name;        this.age = age;    }        @Override    protected Object clone() throws CloneNotSupportedException {    return super.clone();    }

get set 略

将

Professor p2=p;

修改为

 Professor p2=(Professor) p.clone();

测试后发现显示的name不一样，但这不是深拷贝。比如如果教授实体里面有一个其他对象Student的引用呢？

public class Student {String name;// 常量对象。int age;Student(String name, int age) {this.name = name;this.age = age;}

Student s1 = new Student("zhangsan", 18);    Professor p = new Professor("wangwu", 50,s1);//教授p有学生zhangsan    Professor p2=(Professor) p.clone();    p2.student.name="zhangmin";        System.out.println(p.student.name);    System.out.println(p2.student.name);

发现显示姓名相同，对引用对象student并没有实现深拷贝

那么，怎么实现深拷贝呢？

下面使用序列化实现深拷贝

public class Professor implements Serializable {    String name;    int age;    Student student;     Professor(String name, int age) {        this.name = name;        this.age = age;    }        Professor(String name, int age,Student student) {        this.name = name;        this.age = age;        this.student=student;    }        public Object deepClone() throws IOException, OptionalDataException, ClassNotFoundException {// 将对象写到流里ByteArrayOutputStream bo = new ByteArrayOutputStream();ObjectOutputStream oo = new ObjectOutputStream(bo);oo.writeObject(this);// 从流里读出来ByteArrayInputStream bi = new ByteArrayInputStream(bo.toByteArray());ObjectInputStream oi = new ObjectInputStream(bi);return (oi.readObject());    }    public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}    }

main()

Student s1 = new Student("zhangsan", 18);    Professor p = new Professor("wangwu", 50,s1);//教授p有学生zhangsan    Professor p2=(Professor) p.deepClone();    p2.student.name="zhangmin";        System.out.println(p.student.name);    System.out.println(p2.student.name);

发现显示name不一样。彻底实现了深拷贝。

注意，student也需要序列化，否则会出现错误：Exception in thread "main" java.io.NotSerializableException:

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