objectStream.java

package randomAccess;

import Employee.Employee;
import Employee.Manager;

import java.io.*;


public class objectStream {
    public static void main(String[] args) throws ClassNotFoundException{
        Employee harry = new Employee("harry",50000d,1989,10,1);
        Manager carl = new Manager("carl",8000d,1983,12,22);
        carl.setSecretary(harry);
        Manager tony = new Manager("tony",4000d,1990,3,15);
        tony.setSecretary(harry);
        Employee[] staff = new Employee[3];
        staff[0] = carl;
        staff[1] = harry;
        staff[2] = tony;
        try(ObjectOutputStream out = new ObjectOutputStream((new FileOutputStream("employee.dat")))){
            out.writeObject(staff);
        }catch (IOException e){
            System.out.println(e);
        }
        try(ObjectInputStream in = new ObjectInputStream(new FileInputStream("employee.dat"))){

            Employee[] newStaff = (Employee[])in.readObject();

            //raise secretary's salary

            newStaff[1].raiseSalaryt(10);
            for (Employee e:newStaff
                 ) {
                System.out.println(e);
            }
        }catch (IOException e){

        }
    }
}
##  Employee

package Employee;

import java.io.Serializable;
import java.time.LocalDate;

public class Employee implements Serializable{
private String name;
private double salary;
private LocalDate hireDay;
public Employee(String name,Double salary,int year,int month, int day ){
this.name = name;
this.salary = salary;
this.hireDay = LocalDate.of(year,month,day);
}

public String getName() {
    return name;
}

public double getSalary() {
    return salary;
}

public LocalDate getHireDay() {
    return hireDay;
}

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

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

public void setHireDay(LocalDate hireDay) {
    this.hireDay = hireDay;
}
public void raiseSalaryt(double byPercent){
    double raise = salary*byPercent/100;
    salary+=raise;
}

@Override
public String toString() {
    return "Employee{" +
            "name='" + name + '\'' +
            ", salary=" + salary +
            ", hireDay=" + hireDay +
            '}';
}

}

Manager

package Employee;

import java.io.Serializable;

public class Manager extends Employee implements Serializable{
    private double bouns;
    private Employee secretary;

    public void setSecretary(Employee secretary) {
        this.secretary = secretary;
    }

    public Manager(String name, double salary, int year, int month, int day) {
        super(name,salary,year,month,day);
        bouns = 0;
    }
    public double getSalary(){
        double baseSalary = super.getSalary();
        return baseSalary+bouns;
    }
    public void setBouns(double d){
        bouns = d;
    }
}

运行结果截图

image.png