声明:下面代码为仿照视频所有,因为笔误原因,发现了个问题,原因不明,哪位朋友看后帮忙解释一下,谢谢
1
import java.lang.reflect.Field;
2import java.lang.reflect.Method;
3
4
public class ReflctTester 
{
5
6
public Object copy(Object object) throws Exception{
7 Class<?> classType = object.getClass();
8 System.out.println("Class :"+ classType.getName());
9 //默认构造方法必须为public,不明白为什么换作friendly,protected却不行,而显示的构造方法却可以
10 Object objectCopy = classType.getConstructor(new Class[]{}).newInstance(new Object[]{});
11 Field fields[] = classType.getDeclaredFields();
12 for(int i=0;i<fields.length;i++){
13 Field field = fields[i];
14 String fieldName = field.getName();
15 String firstLetter = fieldName.substring(0,1).toUpperCase();
16 String getMethodName = "get"+firstLetter+fieldName.substring(1);
17 String setMethodName = "set"+firstLetter+fieldName.substring(1);
18 Method getMethod = classType.getMethod(getMethodName,new Class[]{});
19 Method setMethod = classType.getMethod(setMethodName, new Class[]{field.getType()});
20 Object value = getMethod.invoke(object, new Object[]{});
21 System.out.println(fieldName+":" + value);
22 setMethod.invoke(objectCopy,new Object[]{value});
23
}
24 return objectCopy;
25 }
26
27 public static void main(String[] args) throws Exception {
28 Customer customer = new Customer("Tom", 21);
29 customer.setId(new Long(1));
30 Customer customerCopy = (Customer) new ReflctTester().copy(customer);
31 System.out.println("Copy information:" + customerCopy.getId() + " " + customerCopy.getName() + " " +customerCopy.getAge());
32 }
33
34
}
35
36class Customer{
37 private Long id;
38 private String name;
39 private int age;
40 protected Customer(){}
41 public Customer(String name,int age){
42 this.name = name;
43 this.age = age;
44 }
45 public int getAge() {
46 return age;
47 }
48 public void setAge(int age) {
49 this.age = age;
50 }
51 public Long getId() {
52 return id;
53 }
54 public void setId(Long id) {
55 this.id = id;
56 }
57 public String getName() {
58 return name;
59 }
60 public void setName(String name) {
61 this.name = name;
62 }
63}
上面的例子中如果默认的构造方法不为public则报
Exception in thread "main" java.lang.NoSuchMethodException: <init>()异常
问一个朋友得知:<init>()这个就是默认构造方法的签名
而<cinit>() 是类的初始化方法签名,第一次加载类时报错