Lintcode455-StudentID-Easy

Implement a class Class with the following attributes and methods:

1. A public attribute students which is a array of Student instances.
2. A constructor with a parameter n, which is the total number of students in this class. The constructor should create n Student instances and initialized with student id from 0 ~ n-1

Example

Example 1:

Input: 3
Output: [0, 1, 2]
Explanation: For 3 students, your cls.students[0] should equal to 0, cls.students[1] should equal to 1 and the cls.students[2] should equal to 2.

Example 2:

Input: 5
Output: [0, 1, 2, 3, 4]

注意：

1. 数组的声明和创建：数组声明不能制定大小（因为只是创建了一个引用变量），数组创建时必须制定大小！
2. Java 对象和对象的引用
3. Class类：先声明一个数组类型的引用变量，在构造方法中才能使引用变量指向创建的数组，因为有了参数n,知道数组长度后,才能创建数组。

代码：

class Student {
    public int id;

    public Student(int id) {
        this.id = id;
    }
}

public class Class {
    public Student[] students; // 声明Student类型数组，即创建一个引用

    public Class(int n) {
        this.students = new Student[n]; // 创建Student类型数组，将引用（students）指向此数组
        for (int i = 0; i < n; i++) {
            students[i] = new Student(i);
        }
    }
}