java - "p"无法解析为变量

Question

我必须使用 switch 语句来允许用户选择他们想要执行的操作，如果他们选择“1”，则将允许他们将一个人添加到数据库中。在“1”的 switch 语句中，我收到一个语法错误，指出“p”无法解析为变量。然而，我已经尝试了我能想到的一切来让它发挥作用，但它不会。有什么想法吗？

package hartman;

import java.util.ArrayList;
import java.util.Scanner;

public class Main {

public static void main(String[] args) {
    Printer.printWelcome();

    Scanner keyboard = new Scanner(System.in);
    ArrayList<Person> personList = new ArrayList<>();
    boolean keepRunning = true;
    while (keepRunning) {
        Printer.printMenu();
        Printer.printPrompt("Please enter your operation: ");

        String userSelection = keyboard.nextLine();

        switch (userSelection) {
        case "1":
            Database.addPerson(p);
            break;
        case "2":
            Database.printDatabase(personList);
            break;
        case "3":
            Printer.printSearchPersonTitle();
            String searchFor = keyboard.nextLine();
            Database.findPerson(searchFor);
            break;
        case "4":
            keepRunning = false;
            break;
        default:
            break;
        }
    }

    Printer.printGoodBye();
    keyboard.close();
}

 }

这是Database.java -

package hartman;

import java.util.ArrayList;
import java.util.Scanner;

public class Database {
static Scanner keyboard = new Scanner(System.in);
private static ArrayList<Person> personList;

public Database() {

}

public static void addPerson(Person personList2) {
    Printer.printAddPersonTitle();
    Printer.printPrompt("  Enter first name: ");
    String addFirstName = keyboard.nextLine();

    Printer.printPrompt("  Enter last Name: ");
    String addLastName = keyboard.nextLine();

    Printer.printPrompt("  Enter social Security Number: ");
    String addSocial = keyboard.nextLine();

    Printer.printPrompt("  Enter year of birth: ");
    int addYearBorn = Integer.parseInt(keyboard.nextLine());

    System.out.printf("\n%s, %s saved!\n", addFirstName, addLastName);

    Person person = new Person();
    person.setFirstName(addFirstName);
    person.setLastName(addLastName);
    person.setSocialSecurityNumber(addSocial);
    person.setYearBorn(addYearBorn);
    personList.add(personList2);
}

    public static void printDatabase(ArrayList<Person> personList) {
    System.out
            .printf("\nLast Name           First Name           Social Security Number  Age\n");
    System.out
            .printf("=================== ===================  ======================  ===\n");
    for (Person p : personList) {

        System.out.printf("%-20s%-21s%-24s%s\n", p.getLastName(),
                p.getLastName(), p.getSocialSecurityNumber(),          p.getAge());

    }

}

public static ArrayList<Person> findPerson(String searchFor) {
    ArrayList<Person> matches = new ArrayList<>();
    for (Person p : personList) {
        boolean isAMatch = false;

        if (p.getFirstName().equalsIgnoreCase(searchFor)) {
            isAMatch = true;

        }
        if (p.getLastName().equalsIgnoreCase(searchFor)) {
            isAMatch = true;

        }
        if (p.getSocialSecurityNumber().contains(searchFor)) {
            isAMatch = true;
            ;
        }
        if (String.format("%d", p.getAge()).equals(searchFor))
            if (isAMatch) {

            }
        matches.add(p);
    }
    return matches;

}

}

Answer 1

编译器无法将 p 解析为变量，因为您在任何地方都没有声明 p。

更好的解决方案:

我认为直接在数据库中进行人员创建过程要好得多，因此请执行以下操作: 将 Database.java 更改为:

public static void addPerson() {
Printer.printAddPersonTitle();
Printer.printPrompt("  Enter first name: ");
String addFirstName = keyboard.nextLine();

Printer.printPrompt("  Enter last Name: ");
String addLastName = keyboard.nextLine();

Printer.printPrompt("  Enter social Security Number: ");
String addSocial = keyboard.nextLine();

Printer.printPrompt("  Enter year of birth: ");
int addYearBorn = Integer.parseInt(keyboard.nextLine());

System.out.printf("\n%s, %s saved!\n", addFirstName, addLastName);

Person person = new Person();
person.setFirstName(addFirstName);
person.setLastName(addLastName);
person.setSocialSecurityNumber(addSocial);
person.setYearBorn(addYearBorn);
personList.add(person);
}

将第一个代码更改为:

Database.addPerson();