关于getConstructors()跑出数组异常的问题

package StudyOne;

import java.lang.reflect.Constructor;

class students{
private String name;
private int age;
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 "我的名字叫"+this.name+"今年"+this.age+"岁";

}
}

public class BeansOne {
public static void main(String[] args) throws Exception{
Class clazz=Class.forName("StudyOne.students");
Constructor cons[]=clazz.getConstructors();
students s=(students) cons[0].newInstance("张三",30);
System.out.println(s);
}
}
执行后会抛出一个Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0的异常。

1. package StudyOne ----Java的包名是小写的，类似package java.util; 2.class students-----Java的类名是大写的 3.加一个构造函数

下面是可以运行的：

package com.eei.common;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;

/**

• Created by luoqi on 2016/3/14.
  */
  public class Student {

  private String name;
  private int age;

  public Student(String name,int age){
  this.age = age;
  this.name = name;
  }

  public int getAge() {
  return age;
  }

  public void setAge(int age) {
  this.age = age;
  }

  public String getName() {

  return name;
  

  }

  public void setName(String name) {
  this.name = name;
  }

  public String toString() {
  return "我的名字叫" + this.name + "今年" + this.age + "岁";
  }

  public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InvocationTargetException, InstantiationException {
  Class clazz=Class.forName("com.eei.common.Student");
  Constructor cons[]=clazz.getConstructors();
  Student s=(Student) cons[0].newInstance("张三",30);
  System.out.println(s);
  }
  }

这是一个数组下标异常，我想知道他为什么会出现一个 数组下标异常。