java中不显式调用toString()的输出信息

Question

对于 println 中的第 6 步，我知道如何显式调用 toString 但如何在不显式调用 toString() 或使用任何访问器方法的情况下从数组中的当前学生输出学生信息？

import java.util.Scanner;

public class Students
{
  private static Scanner input = new Scanner(System.in);

  public static void main(String[] args)
  {
    Student[] students;

    students = getStudents();
    printStudents(students);
  }

  private static Student[] getStudents()
  {
    Student[] temp;
    int       how_many;

    System.out.print("How many students? ");
    how_many = input.nextInt();
    purgeInputBuffer();
    temp =  new Student[input.nextInt()];  // Step 1 ???
    for (int i = 0; i < temp.length; i++)
    {
      getStudent();
      temp[i] = getStudent();     // Step 2
    }
    return temp;    // Step 3
  }

  private static Student getStudent()
  {
    String name,
           address,
           major;
    double gpa;

    System.out.print("Enter name: ");
    name = input.nextLine();
    System.out.print("Enter address: ");
    address = input.nextLine();
    System.out.print("Enter major: ");
    major = input.nextLine();
    System.out.print("Enter GPA: ");
    gpa = input.nextDouble();
    purgeInputBuffer();

    return new Student(name, address, major, gpa);     // Step 4
  }

  private static void printStudents(Student[] s)
  {
    System.out.println();
    for (int i = 0; i < s.length; i++)    // Step 5
    {
      System.out.println(______);     // Step 6
    }
  }

  private static void purgeInputBuffer()
  {
    // ----------------------------------------------------
    // Purge input buffer by reading and ignoring remaining
    // characters in input buffer including the newline
    // ----------------------------------------------------
    input.nextLine();
  }
}

Answer 1

1. 将变量name, address, major, gpa为成员变量。

2. 覆盖此类的toString()方法。

    public String toString() { return "Name: " + name + "\\n" + "Address: " + .... //whatever you want to print. }

3. 每当您需要打印学生的详细信息时，请将其传递给println方法：

    System.out.println(obj); //where obj is a Student object.

Answer 2

• 在您的Stundent类中重写toString()方法，例如：

   @Override public String toString() { return "Stundent [ Name: " + name + ", Address: " + address + ", Major: " + major + ", GPA: " + gpa + " ]"; }

• 并修改您的printStudents()方法如下（您的第 6 步）：

   private static void printStudents(final Student[] s) { System.out.println(); for (final Student student : s) { System.out.println(student); } }

• 那么你的输出应该是这样的：

学生 [姓名：Name1，地址：Addr1，专业：Major1，GPA：3.0]
学生 [姓名：Name2，地址：Addr2，专业：Major2，GPA：3.5]

现在您看到toString()方法将被隐式调用。