Java 如何从序列化的arraylist中拾取某些对象?
在选项2和选项3中,我不知道如何为某些数据类型I.e引用序列化的arraylist。字符串last name或double gpa,然后比较它们。在实验单上,我们得到了关于如何做其他事情的说明,但对于做选项2和选项3,它实际上是在说“弄明白”,教授从来都不善于向全班解释事情。所以我希望有人能给我解释一下 编辑:901号是我所在大学的学号 这是我的学生班,里面的一切都应该很好Java 如何从序列化的arraylist中拾取某些对象?,java,serialization,Java,Serialization,在选项2和选项3中,我不知道如何为某些数据类型I.e引用序列化的arraylist。字符串last name或double gpa,然后比较它们。在实验单上,我们得到了关于如何做其他事情的说明,但对于做选项2和选项3,它实际上是在说“弄明白”,教授从来都不善于向全班解释事情。所以我希望有人能给我解释一下 编辑:901号是我所在大学的学号 这是我的学生班,里面的一切都应该很好 import java.io.Serializable; public class Student implements
import java.io.Serializable;
public class Student implements Serializable
{
private String lastName, firstName;
private double gpa;
private int studentID, gradYear;
public Student(int studentID, String lastName, String firstName, double gpa, int gradYear)
{
this.studentID = studentID;
this.lastName = lastName;
this.firstName = firstName;
this.gpa = gpa;
this.gradYear = gradYear;
}
public int getStudentID()
{
return studentID;
}
public String getLastName()
{
return lastName;
}
public String getFirstName()
{
return firstName;
}
public double getGPA()
{
return gpa;
}
public int getGradYear()
{
return gradYear;
}
public String toString()
{
return "Student ID: " + studentID + " Name: " + lastName.trim() + ", " + firstName.trim() + " GPA: " + gpa + " Grad year: " + gradYear;
}
}
这是一个测试类,我需要选项2和3之外的帮助,我认为这一切都是可行的
import java.util.*;
import java.io.*;
public class StudentTestOS
{
public static void main(String[] args) throws IOException, ClassNotFoundException
{
boolean done = false;
ArrayList<Student> sList = new ArrayList<Student>();
File sFile = new File("studentOS.dat");
if(sFile.exists())
{
FileInputStream myFIS = new FileInputStream(sFile);
ObjectInputStream sIn = new ObjectInputStream(myFIS);
sList = (ArrayList<Student>)sIn.readObject();
sIn.close();
}
System.out.println("Students on file: ");
for(int i = 0; i < sList.size(); i++)
System.out.println(sList.get(i).toString());
do
{
Scanner myScanner = new Scanner(System.in);
while (!done)
{
System.out.println("1 - add a student");
System.out.println("2 - display student info");
System.out.println("3 - display student info given their last name");
System.out.println("4 - exit");
int choice = Integer.parseInt(myScanner.nextLine());
if (choice == 1)
{
System.out.print("Enter 901 number: ");
int studentID = Integer.parseInt(myScanner.nextLine());
System.out.print("Enter last name: ");
String lastName = myScanner.nextLine();
System.out.print("Enter first name: ");
String firstName = myScanner.nextLine();
System.out.print("Enter gpa: ");
double gpa = Double.parseDouble(myScanner.nextLine());
System.out.print("Enter grad year: ");
int gradYear = Integer.parseInt(myScanner.nextLine());
Student myStudent = new Student(studentID, lastName, firstName, gpa, gradYear);
sList.add(myStudent);
}
else if (choice == 2)
{
System.out.print("Enter 901 number: ");
int studentID = Integer.parseInt(myScanner.nextLine());
}
else if (choice == 3)
{
System.out.println("Enter last name: ");
String lastName = myScanner.nextLine();
}
else if (choice == 4)
{
done = true;
}
else
System.out.println("Invalid menu choice!");
}
System.out.println("Goodbye!");
}while(!done);
FileOutputStream myFOS = new FileOutputStream(sFile);
ObjectOutputStream sOut = new ObjectOutputStream(myFOS);
sOut.writeObject(sList);
sOut.close();
}
}
您可以创建一个循环,并在choice2的给定属性Id和Choice3的lastName上逐个比较对象 选择2:-
System.out.print("Enter 901 number: ");
int studentID = Integer.parseInt(myScanner.nextLine());
for(Student student : sList){
if(student.getStudentID == studentId){
System.out.println(student);
break; // As student Id is unique.So, once we found the student no need to loop further.
}
}
对于选项3,将其与lastName进行比较,不要使用break语句,因为可能有许多具有相同lastName的语句