Java集合排序练习4-4，烦请老师检查并指正～

老师，好奇怪，我每次在线都运行出错，但是在Eclipse是成功的～

package com.imooc.array.comparable;

public class Employee implements Comparable<Employee> {
	private String emNum;
	private String name;
	private double salary;

	public Employee() {

	}

	public Employee(String emNum, String name, double salary) {
		this.setEmNum(emNum);
		this.setName(name);
		this.setSalary(salary);
	}

	public String getEmNum() {
		return emNum;
	}

	public void setEmNum(String emNum) {
		this.emNum = emNum;
	}

	public String getName() {
		return name;
	}

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

	public double getSalary() {
		return salary;
	}

	public void setSalary(double salary) {
		this.salary = salary;
	}

	@Override
	public String toString() {
		return "Employee [emNum=" + emNum + ", name=" + name + ", salary=" + salary + "]";
	}

	@Override
	public int compareTo(Employee o) {
		double s1 = this.getSalary();
		double s2 = o.getSalary();
		int n = new Double(s2 - s1).intValue();
		return n;
	}

}

​package com.imooc.array.comparable;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class TestEmployee {

	public static void main(String[] args) {
		Employee emp1 = new Employee("emp001", "Peter", 1800);
		Employee emp2 = new Employee("emp002", "Sherry", 2500);
		Employee emp3 = new Employee("emp003", "Angel", 1600);
		List <Employee> list = new ArrayList <Employee> ();
		list.add(emp1);
		list.add(emp2);
		list.add(emp3);
		System.out.println("Before:");
		for(Employee emp: list) {
			System.out.println(emp);
		}
		Collections.sort(list);
		System.out.println("After:");
		for(Employee emp: list) {
			System.out.println(emp);
		}

	}

}