员工管理系统（集合与IO流的结合使用 beta4.0 ObjectInputStream/ ObjectOutputStream）

 package cn.employee_io;

 import java.io.Serializable;

 public class Employee implements Serializable{
     /**
      *
      */
     private static final long serialVersionUID = 1L;
     private String empId;
     private String name;
     private int age;
     private double salary;

     public Employee() {
         super();
     }

     public Employee(String empId, String name, int age, double salary) {
         super();
         this.empId = empId;
         this.name = name;
         this.age = age;
         this.salary = salary;
     }

     public String getEmpId() {
         return empId;
     }

     public void setEmpId(String empId) {
         this.empId = empId;
     }

     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 double getSalary() {
         return salary;
     }

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

     @Override
     public int hashCode() {
         final int prime = 31;
         int result = 1;
         result = prime * result + ((empId == null) ? 0 : empId.hashCode());
         return result;
     }

     @Override
     public boolean equals(Object obj) {
         if (this == obj)
             return true;
         if (obj == null)
             return false;
         if (getClass() != obj.getClass())
             return false;
         Employee other = (Employee) obj;
         if (empId == null) {
             if (other.empId != null)
                 return false;
         } else if (!empId.equals(other.empId))
             return false;
         return true;
     }

     public String toString() {
         return empId + "," + name + "," + age+ "," + salary;
     }

 }

Employee.java

 package cn.employee_io;

 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.util.LinkedList;
 import java.util.List;

 public class Service {
     List<Employee> list = new LinkedList<Employee>();
     File file = null;
     ObjectInputStream ois = null;
     ObjectOutputStream oos = null;
     boolean flag=false;

     public Service() throws IOException, ClassNotFoundException {
         reader();
     }

     /**
      * 读文件
      * @throws IOException
      * @throws ClassNotFoundException
      */
     @SuppressWarnings("unchecked")
     public void reader() throws IOException, ClassNotFoundException {//ObjectInputStream先写后读
         file = new File("src/cn/employee_io/emp.txt");
         if (!file.exists()) {
             writer();
         }else{
             ois = new ObjectInputStream(new FileInputStream(file));
             list = (List<Employee>) ois.readObject(); // 给list赋值
             ois.close();
         }
     }

     /**
      * 写文件
      * @throws IOException
      * @throws ClassNotFoundException
      */
     public void writer() throws IOException, ClassNotFoundException {
         file = new File("src/cn/employee_io/emp.txt");
         oos = new ObjectOutputStream(new FileOutputStream(file));
         oos.writeObject(list);
         oos.flush();
         oos.close();
     }

     /**
      * 添加员工
      * @param e
      * @throws ClassNotFoundException
      * @throws IOException
      */
     public void add(Employee e) throws ClassNotFoundException, IOException {
         if (!list.contains(e)) {
             list.add(e);
             writer();
             System.out.println("添加成功！");
         } else {
             System.out.println("添加失败！");
         }
     }

     /**
      * 查询所有员工
      */
     public void queryAll(){
         System.out.println("编号          "+"姓名          "+"年龄          "+"薪资");
         for(Employee e:list){
             System.out.println(e.getEmpId()+"  "+e.getName()+"  "+e.getAge()+"  "+e.getSalary());
         }
     }

     /**
      * 查询单个员工
      * @param empId
      */
     public void query(String empId){
         for(int i=0;i<list.size();i++){
             if(list.get(i).getEmpId().equals(empId)){
                 System.out.println("编号          "+"姓名          "+"年龄          "+"薪资");
                 System.out.println(list.get(i).getEmpId()+"  "+list.get(i).getName()+"  "+list.get(i).getAge()+"  "+list.get(i).getSalary());
             }
         }
     }

     /**
      * 删除员工
      * @throws IOException
      * @throws ClassNotFoundException
      */
     public void delete(String empId) throws ClassNotFoundException, IOException{
         for(int i=0;i<list.size();i++){
             if(list.get(i).getEmpId().equals(empId)){
                 list.remove(list.get(i));
                 writer();
                 System.out.println("删除成功！");
                 break;
             }
             if((i==list.size()-1)&&(!list.get(i).getEmpId().equals(empId))){
                 System.out.println("删除失败！");
             }
         }
     }

     /**
      * 修改员工
      * @throws IOException
      * @throws ClassNotFoundException
      */
     public void update(Employee emp) throws ClassNotFoundException, IOException{
         for(int i=0;i<list.size();i++){
             if(list.get(i).getEmpId().equals(emp.getEmpId())){
                 list.get(i).setName(emp.getName());
                 list.get(i).setAge(emp.getAge());
                 list.get(i).setSalary(emp.getSalary());
                 writer();
                 System.out.println("修改成功！");
             }
             if((i==list.size()-1)&&(!list.get(i).getEmpId().equals(emp.getEmpId()))){
                 System.out.println("修改失败！");
             }
         }
     }
 }

Service.java

 package cn.employee_io;

 import java.io.IOException;
 import java.util.Scanner;

 public class TestEmp {
     static Scanner sc = new Scanner(System.in);    

     static String empId;
     static String name;
     static int age;
     static double salary;
     static int num;

     public static void main(String[] args) throws ClassNotFoundException, IOException {
         Service s=new Service();

         ok: for (;;) {
             printOptions();
             num = sc.nextInt(); 

             if (num < 1 || num > 6) {
                 System.out.println("输入有误，将重新开始选择！");
                 break ok;
             }

             switch (num) {
             case 1:
                 printEmpNo();
                 printName();
                 s.add(new Employee(empId,name,age,salary));
                 break;
             case 2:
                 s.queryAll();
                 break;
             case 3:
                 printEmpNo();
                 s.query(empId);
                 break;
             case 4:
                 printEmpNo();
                 s.delete(empId);
                 break;
             case 5:
                 printEmpNo();
                 printName();
                 s.update(new Employee(empId,name,age,salary));
                 break;
             case 6:
                 return;
             }
         }
     }

     public static void printOptions() {
         System.out.println("***员工管理系统***");
         System.out.println("1.添加员工");
         System.out.println("2.查询所有员工");
         System.out.println("3.查询员工");
         System.out.println("4.删除员工");
         System.out.println("5.修改员工");
         System.out.println("6.退出");
         System.out.println("请输入你要进行的操作：");
     }

     public static void printEmpNo() {
         System.out.println("请输入员工编号：");
         empId = sc.next();
     }

     public static void printName() {
         System.out.println("请输入员工姓名：");
         name = sc.next();
         System.out.println("请输入员工年龄：");
         age = sc.nextInt();
         System.out.println("请输入员工薪资：");
         salary=sc.nextDouble();
     }
 }

TestEmp.java