怎么还是报错呢？ - 黑马程序员技术交流社区

package com.itheima.fans;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
public class Demo4 {
/**
* 通过Class调用其他类中的构造函数 ,
* 也可以通过这种方式通过Class创建其他类的对象
*/
public static void main(String[] args) {
Class demo=null;
try {
demo=Class.forName("com.itheima.fans.Person");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Person per1=null;
Person per2=null;
Person per3=null;
Person per4=null;
//取得全部的构造函数
Constructor<?> cons[]=demo.getConstructors();
System.out.println(cons.length);
try {
per1=(Person)cons[0].newInstance();
per2=(Person)cons[1].newInstance("zhangsan");
per3=(Person)cons[2].newInstance(25);
per4=(Person)cons[3].newInstance("zhangsan",25);
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(per1);
System.out.println(per2);
System.out.println(per3);
System.out.println(per4);
}
}
class Person{
private String name;
private int age;
public Person() {
}
public Person(String name){
this.name=name;
}
public Person(int age){
this.age=age;
}
public Person(String name, int age) {
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 String toString(){
return "["+this.name+" "+this.age+"]";
}
}

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