class Address{
public Address(){
}
public Address(String state, int number){
this.number = number;
this.state = state;
}
@Override
public String toString(){
return "state: " + state + " munber: " + number;
}
public String getState(){
return state;
}
public void setState(String state){
this.state = state;
}
public int getNumber(){
return number;
}
public void setNumber(int number){
this.number = number;
}
private String state;
private int number;
}
public class Employee implements Cloneable{
public Employee(){
}
public Employee(String name, int age, Address address){
this.address = address;
this.age = age;
this.name = name;
}
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;
}
public Address getAddress(){
return address;
}
public void setAddress(Address address){
this.address = address;
}
@Override
public String toString(){
StringBuilder sb = new StringBuilder();
sb.append("name:" + name + ", ");
sb.append("age:" + age + " \n");
sb.append("Address: " + address);
return sb.toString();
}
@Override
protected Employee clone(){
Employee employee = null;
try{
employee = (Employee) super.clone();
}catch(CloneNotSupportedException e){
e.printStackTrace();
}
return employee;
} private String name;
private int age;
private Address address;
public static void main(String[] args){
System.out.println("克隆之前:");
Address add1 = new Address("中国", 1);
Employee emp1 = new Employee("rollen", 20, add1);
System.out.println(emp1);
System.out.println("克隆之后");
Employee emp2 = emp1.clone();
System.out.println("====重新设置对象emp2值=====");
emp2.setName("hello world");
emp2.setAge(100);
//emp2.address.setNumber(2);//
//emp2.address.setState("美国");//原始类的赋值方法
emp2.setAddress(new Address("美国", 2));//本类中的set方法####
System.out.println(emp1);
System.out.println("-----");
System.out.println(emp2);
}
}
在博客园看到一篇文章,顺手就做了个测试,发现一个问题,就是一个类用用另外一个类的对象作为成员变量时,用来的原始类的set方法给每个变量赋值是可以,但是要用在该类中直接用本类的set方法对对象进行赋值,就是不能赋值成功,我debug了一下,看到值的变化后很奇怪(在####处执行setAddress()方法时,也能看到会把new对象的新值带过去,但是一跳到main函数就是不能带回来),有那位大神解释一下。
第一次第二次 都是输出的emp1对象,只是克隆前和克隆后,你程序没有修改emp1的值,自然是一样的。
而emp2你主动改了属性,所以都改了,一切都很正常。你觉得哪里奇怪?
emp2.address.setNumber(2);//
emp2.address.setState("美国");//原始类的赋值方法
却和
emp2.setAddress(new Address("美国", 2));
两个执行的结果不一样,这是为什么?
当代码中注释掉
//emp2.address.setNumber(2);//
//emp2.address.setState("美国");//原始类的赋值方法
emp2.setAddress(new Address("美国", 2));
打印结果符合预期的
克隆之前:
name:rollen, age:20
Address: state: 中国 munber: 1
克隆之后
====重新设置对象emp2值=====
name:rollen, age:20
Address: state: 中国 munber: 1
-----
name:hello world, age:100
Address: state: 美国 munber: 2反之
当代码中注释掉
emp2.address.setNumber(2);//
emp2.address.setState("美国");//原始类的赋值方法
//emp2.setAddress(new Address("美国", 2));
克隆之前:
name:rollen, age:20
Address: state: 中国 munber: 1
克隆之后
====重新设置对象emp2值=====
name:rollen, age:20
Address: state: 美国 munber: 2
-----
name:hello world, age:100
Address: state: 美国 munber: 2
也就是说emp2.address.setState("美国")也改变了emp1的state 的值,emp2.address.setNumber(2)同理,这是为什么?
emp1.adress和emp2.address指向同一个对象
所以emp2.address.setXXX();改变emp2.address指向的对象的属性,emp1.address当然能看到变量了,因为它们看到是同一个对象
而emp2.setAddress(new Address("美国", 2));
是把emp2.address指向另一个新的new Address("美国", 2)对象,也就是说此时emp1.address和emp2.address不再指向相同的对象,那么emp2.adress怎么变化,也不会影响emp1.address,因为它们引用的是不同的两个对象。