Java I/O读取和解析.emp文件示例

• 1.使用到的知识点
• 2.示例1
• • 2.1存储几个员工数据到不同的文件
  • • 2.1.1题目要求
    • 2.1.2相关代码
    • 2.1.3结果展示
  • 2.2读取存储数据的文件
  • • 2.2.1题目要求
    • 2.2.2相关代码
    • 2.2.3结果展示
  • 2.3获得入职20周年纪念日派对日期
  • • 2.3.1题目要求
    • 2.3.2相关代码
    • 2.3.4结果展示
• 3.示例2
• • 3.1获取Emp.dat文件
  • 3.2题目要求
  • 3.2.1相关代码
  • 3.2.2结果展示

1.使用到的知识点

IO流
存数据和读数据
集合
用来存储解析的数据，对数据进行相关操作
文件操作
创建相关的文件存储数据

2.示例1

2.1存储几个员工数据到不同的文件

2.1.1题目要求

要求用户输入一个员工信息，格式为：
name,age,gender,salary,hiredate
例如:
张三,25,男,5000,2006-02-15
然后将输入的员工信息解析成Emp对象。
然后将该Emp对象的toString返回的字符串写入到文件中，该文件的
名字为:name.emp,以上面的例子，那么该文件名为:张三.emp
至少运行5次该程序，输入五个员工信息，并生成5个文件。

2.1.2相关代码

public class Exercise15 {
    public static void main(String[] args) throws Exception {
        Scanner scanner = new Scanner(System.in);
        System.out.println("输入员工信息：");
        String message = scanner.next();
        Emp object = getObject(message);
        System.out.println(object);
        saveData(object);
    }
    //解析输入的员工对象信息
    private static Emp getObject(String string) throws ParseException {
        String[] str = string.split(",");
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Emp emp = new Emp(str[0], Integer.parseInt(str[1]), str[2], Double.parseDouble(str[3]), sdf.parse(str[4]));
        return emp;
    }
    //保存数据
    private static void saveData(Emp emp) throws IOException {
        String name = emp.getName();
        File file = new File(name+".emp");
        if (!file.exists()) {
            file.createNewFile();
        }
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(file));
        oos.writeObject(emp);
        oos.close();
        System.out.println("存入数据成功！");
    }
}
class Emp implements Serializable {

    private String name;
    private int age;
    private String gender;
    private double salary;
    private Date hireDate;

    public Emp() {
    }

    public Emp(String name, int age, String gender, double salary, Date hireDate) {
        this.name = name;
        this.age = age;
        this.gender = gender;
        this.salary = salary;
        this.hireDate = hireDate;
    }

    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 getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public double getSalary() {
        return salary;
    }

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

    public Date getHireDate() {
        return hireDate;
    }

    public void setHireDate(Date hireDate) {
        this.hireDate = hireDate;
    }

    @Override
    public String toString() {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        return name+","+age+","+name+","+salary+","+sdf.format(hireDate);
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Emp emp = (Emp) o;
        return age == emp.age &&
                Double.compare(emp.salary, salary) == 0 &&
                Objects.equals(name, emp.name) &&
                Objects.equals(gender, emp.gender) &&
                Objects.equals(hireDate, emp.hireDate);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, age, gender, salary, hireDate);
    }
}

2.1.3结果展示

2.2读取存储数据的文件

2.2.1题目要求

编写一个程序，将当前目录下所有员工文件进行读取，并解析出所有员工为Emp
对象并存入集合。然后排序该集合，按照员工的年龄排序，年龄大的靠前，年龄小的靠后。排序完毕后输出结果。

2.2.2相关代码

public class Exercise16 {
    public static void main(String[] args) throws Exception {
        System.out.println("得到相关文件：");
        File[] files = getFiles();
        for (File file : files) {
            System.out.println(file.getName());
        }
        System.out.println("读取数据并查看：");
        List<Emp> list = readData(files);
        for (Emp emp : list) {
            System.out.println(emp);
        }
        System.out.println("根据年龄降序：");
        sortData(list);
        Iterator<Emp> i = list.iterator();
        while (i.hasNext()) {
            System.out.println(i.next());
        }
    }
    //根据年龄排序
    private static void sortData(List<Emp> list){
        Collections.sort(list, (o1, o2) -> o2.getAge()-o1.getAge());
    }
    //得到存入数据的文件
    private static File[] getFiles(){
        File file = new File("./");
        File[] files = file.listFiles(file1 -> file1.getName().endsWith(".emp"));
        return files;
    }
    //读出数据存入到集合中
    private static List<Emp> readData(File[] files) throws Exception {
        List<Emp> list = new ArrayList<>();
        ObjectInputStream ois = null;
        for (File file : files) {
            ois = new ObjectInputStream(new FileInputStream(file));
            Object object=ois.readObject();
            if (object instanceof Emp) {
                Emp p = (Emp)object;
                list.add(p);
            }
        }
        ois.close();
        System.out.println("读取成功！");
        return list;
    }
}

2.2.3结果展示

2.3获得入职20周年纪念日派对日期

文件获取：emp.dat文件
提取码: vf6a
复制这段内容后打开百度网盘手机App，操作更方便哦

2.3.1题目要求

编写一个程序，将当前目录下所有的员工文件进行读取，并解析出所有员工为Emp
对象并存入Map。其中key为该员工的名字，value为该员工的emp对象。
然后，要求用户输入一个员工名字，若该员工存在，则输出该员工的名字，年龄，工资，以及入职20周年的纪念日当周的周六的日期。
即:输入名字"张三"
若该员工存在，则输出如下格式:
张三,25,5000,2006-02-14
入职20周年纪念日派对日期: 2026-02-14 （注:若入职日期为:2006-02-14）
若该员工不存在，则输出:“查无此人”

2.3.2相关代码

public class Exercise17 {
    private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) throws Exception {
        File[] files = getFiles();
        System.out.println("得到存入数据的文件名：");
        for (File file : files) {
            System.out.println(file.getName());
        }
        Map<String, Emp> data = getData(files);
        System.out.println("遍历map中的数据：");
        Set<Map.Entry<String, Emp>> entries = data.entrySet();
        for (Map.Entry<String, Emp> entry : entries) {
            System.out.println(entry.getKey() + ":" + entry.getValue());
        }
//        data.forEach((s, emp) -> System.out.println(s+":"+emp));
        System.out.println("请输入一个员工的名字：");

        String name = scanner.next();

        getMessage(data, name);
    }

    //判断一个员工存在，存在并输出对应信息和入职纪念日
    private static void getMessage(Map<String, Emp> map, String name) {
        Set<String> set = map.keySet();
        while(true){
        if (!map.containsKey(name)) {
            System.out.println("该员工不存在！");
            System.out.println("请重新输入一个员工的名字：");
            name = scanner.next();
            continue;
        }
        Emp e = map.get(name);
        System.out.println(name + ":" + e);
        Date hireDate = e.getHireDate();
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(hireDate);
        calendar.add(Calendar.YEAR, 20);
        calendar.set(Calendar.DAY_OF_WEEK, Calendar.SATURDAY);
        Date time = calendar.getTime();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String format = sdf.format(time);
        System.out.println("员工入职20周年纪念日派对日期");
        System.out.println(format);
        break;
        }
    }

    //读取存入员工信息的文件名
    private static File[] getFiles() {
        File file = new File("./");
        File[] files = file.listFiles((file1) -> file1.getName().endsWith(".emp"));
        return files;
    }

    //解析文件存到Emp对象中,在将对象存到Map中
    private static Map<String, Emp> getData(File[] files) throws Exception {
        HashMap<String, Emp> map = new HashMap<>();
        ObjectInputStream ois = null;
        for (File file : files) {
            ois = new ObjectInputStream(new FileInputStream(file));
            Object object = ois.readObject();
            if (object instanceof Emp) {
                Emp e = (Emp) object;
                map.put(e.getName(), e);
            }
        }
        return map;
    }
}

2.3.4结果展示

3.示例2

3.1获取Emp.dat文件

3.2题目要求

将emp.dat文件中所有员工解析出来，并创建为若干Emp实例存入一个
集合，然后输出该集合中每个员工信息。
该文件800字节，每80个字节为一个员工的信息。
其中:
name为字符串，长度为32个字节，编码为:UTF-8
age为int,长度为4个字节
gender为字符串，长度为10个字节，编码为:UTF-8
salary为int,长度为4个字节
hiredate为字符串，格式"yyyy-MM-dd"，长度为30个字节，编码为:UTF-8
格式可参考当前包中emp.jpg图
提示:
使用RandomAccessFile读取字符串时，例如name,可以先读取32个字节，再按照UTF-8
转换为字符串，读取age时可以直接使用readInt方法。依次类推。

3.2.1相关代码

public class Exercise18 {
    public static void main(String[] args) throws Exception {
        List<Emp1> data = getData(new File("emp.dat"));
        showData(data);

    }
    //遍历集合中的数据
    private static void showData(List<Emp1> list){
        Iterator<Emp1> i = list.iterator();
        while(i.hasNext()){
            System.out.println(i.next());
        }
//        list.forEach(emp1 -> System.out.println(emp1));
    }
    //读取Emp.dat文件中的员工信息
    private static List<Emp1> getData(File file) throws Exception {
        List<Emp1> list = new LinkedList<>();
        RandomAccessFile raf = new RandomAccessFile(file, "rw");
        if (!file.exists()) {
            return null;
        }
        for (int i = 0; i < 800/80; i++) {
            int number = 80 *i;
            raf.seek(number);
            byte[] bs=new byte[Emp1.NAME];
            String name = new String(bs,0,raf.read(bs));

            raf.seek(number+Emp1.NAME);
            int age = raf.readInt();

            raf.seek(number+Emp1.NAME+Emp1.AGE);
            byte[] bs1=new byte[Emp1.GENDER];
            String gender=new String(bs1,0,raf.read(bs1));

            raf.seek(number+Emp1.NAME+Emp1.AGE+Emp1.GENDER);
            int salary = raf.readInt();

            raf.seek(number+Emp1.NAME+Emp1.AGE+Emp1.GENDER+Emp1.SALARY);
            byte[] bs2=new byte[Emp1.DATE];
            String date=new String(bs2,0,raf.read(bs2));
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            Date hireDate = sdf.parse(date);

            Emp1 e = new Emp1(name, age, gender, salary, hireDate);
            list.add(e);
        }
        return list;
    }

}
class Emp1{
    public static final int NAME=32;
    public static final int AGE=4;
    public static final int GENDER=10;
    public static final int SALARY=4;
    public static final int DATE=30;

    private String name;
    private int age;
    private String gender;
    private int salary;
    private Date hireDate;

    public Emp1() {
    }

    public Emp1(String name, int age, String gender, int salary, Date date) {
        this.name = name;
        this.age = age;
        this.gender = gender;
        this.salary = salary;
        this.hireDate = date;
    }

    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 getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public int getSalary() {
        return salary;
    }

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


    public Date getHireDate() {
        return hireDate;
    }

    public void setHireDate(Date hireDate) {
        this.hireDate = hireDate;
    }


    @Override
    public String toString() {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        return name+","+age+","+gender+","+salary+","+sdf.format(hireDate);
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Emp1 emp1 = (Emp1) o;
        return age == emp1.age &&
                salary == emp1.salary &&
                Objects.equals(name, emp1.name) &&
                Objects.equals(gender, emp1.gender) &&
                Objects.equals(hireDate, emp1.hireDate);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, age, gender, salary, hireDate);
    }
}

3.2.2结果展示