java.util.IllegalFormatConversionException：d = java.lang.String中

Question

我有問題，當使用ArrayList的

package data; 

import java.util.ArrayList; 
import java.util.Collections; 
import java.util.Comparator; 
import java.util.List; 
import java.util.Scanner; 

public class Manager { 
List<Person> p = new ArrayList(); 
Scanner sc = new Scanner(System.in); 

public void addStudent() { 
    String id; 
    String name; 
    int yob; 
    double point1; 
    double point2; 
    System.out.println("Input student id:"); 
    id = sc.nextLine(); 
    System.out.println("Input student name:"); 
    name = sc.nextLine(); 
    System.out.println("Input yob:"); 
    yob = Integer.parseInt(sc.nextLine()); 
    System.out.println("Input point 1:"); 
    point1 = Double.parseDouble(sc.nextLine()); 
    System.out.println("Input point 2:"); 
    point2 = Double.parseDouble(sc.nextLine()); 
    p.add(new Student(id,name,yob,point1,point2)); 
} 
public void addEmployee() { 
    String id; 
    String name; 
    int yob; 
    double salaryRatio; 
    double salary; 
    System.out.println("Input employee id:"); 
    id = sc.nextLine(); 
    System.out.println("Input employee name:"); 
    name = sc.nextLine(); 
    System.out.println("Input employee yob:"); 
    yob = Integer.parseInt(sc.nextLine()); 
    System.out.println("Input salary ratio:"); 
    salaryRatio = Double.parseDouble(sc.nextLine()); 
    System.out.println("Input salary:"); 
    salary = Double.parseDouble(sc.nextLine()); 
    p.add(new Employee(id, name, yob,salaryRatio, salary)); 
} 
public void addCustomer() { 
    String id; 
    String name; 
    int yob; 
    String companyName; 
    double bill; 
    System.out.println("Input customer id:"); 
    id = sc.nextLine(); 
    System.out.println("Input customer name:"); 
    name = sc.nextLine(); 
    System.out.println("Input customer yob:"); 
    yob = Integer.parseInt(sc.nextLine()); 
    System.out.println("Input compnay name:"); 
    companyName = sc.nextLine(); 
    System.out.println("Input bill:"); 
    bill = Double.parseDouble(sc.nextLine()); 
    p.add(new Customer(id,name,yob,companyName,bill)); 
} 
public void addWho() { 
    int choice; 
    do { 
    System.out.println("1.Add Student"); 
    System.out.println("2.Add Employee"); 
    System.out.println("3.Add Customer"); 
    System.out.println("4.Back to menu"); 
    System.out.println("=============="); 
    System.out.println("Choice:"); 
    choice = Integer.parseInt(sc.nextLine()); 
    switch(choice) { 
     case 1: 
      addStudent(); 
      break; 
     case 2: 
      addEmployee(); 
      break; 
     case 3: 
      addCustomer(); 
      break; 
     case 4: 
      break; 
    } 
    } 
    while(choice != 4); 
} 
public void printPersonById() { 
    Collections.sort(p, Comparator.comparing(Person::getId)); 
    for (int i = 0; i < p.size(); i++) { 
     System.out.println(p.get(i)); 
    } 
} 

學生，員工的人打印輸出列表，和客戶是一流的Person.When的子類我嘗試打印列表，他有一個錯誤： 異常線程 「main」 java.util.IllegalFormatConversionException：d = java.lang.String中

我該如何解決呢！？

Answer 1

使用System.out.println(p.get(i).someMethodOrVariableOfPerson);代替System.out.println(p.get(i));

像下面

public void printPersonById() { 
     Collections.sort(p, Comparator.comparing(Person::getId)); 
     for (int i = 0; i < p.size(); i++) { 
      System.out.println("id :"+p.get(i).id); 
      System.out.println("name :"+p.get(i).name); 

     } 
    } 

你不能直接打印Person類對象通過out.println（）方法。 通過out.println（）只允許字符串值

Answer 2

試試這個在您的代碼：

System.out.println("Input yob:"); 
yob = sc.nextInt(); 
System.out.println("Input point 1:"); point1 =sc.nextDouble(); 
System.out.println("Input point 2:"); point2 = sc.nextDouble(); 
p.add(new Student(id,name,yob,point1,point2));