使用扫描器添加到空对象

Question

我试图将用户输入添加到空对象，但我得到null。我想我把扫描仪设置好了，但我不确定。我不确定扫描仪应该如何设置为链接到空对象。我在另一个类上设置了setter和getter。

import java.util.Scanner;
public class StudentRecordTestHarness
{
public static void main (String []args)
{
StudentRecord sr1 = new StudentRecord ("Tim", "Lost", 12345, 75);
System.out.println("First Name: " + sr1.getFirstName());
System.out.println("Last Name: " + sr1.getLastName());
System.out.println("Student ID: " + sr1.getStudentID());
System.out.println("Number Grade for Course: " + sr1.getGradeCourseOne());
System.out.println("Grade Converted to Letter: " + 
sr1.GradeLetter(+sr1.getGradeCourseOne()));
StudentRecord sr2 = new StudentRecord();
Scanner userInput = new Scanner (System.in);
System.out.println("Please Enter Student's First Name: ");
String setFirstName = userInput.nextLine();
System.out.println("New Student First Name: " + sr2.getFirstName());
}
}

Answer 1

您没有设置sr2.firstName;您只是创建了一个新的局部变量setFirstName，它包含了您的输入。

下面设置学生记录的名字:

String setFirstName = userInput.nextLine();
sr2.setFirstName(setFirstName);