如何访问另一个类中的变量，Java？

Question

我有同一个包的多个类，需要访问不同类中的一些变量。如何在汽车类中从carName访问MenuDisplay？感觉我就快到了，但就是想不出来。谢谢

package carrentaltester;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class MenuDisplay {

    public static void displayCarList() {

        String CSVfileName = "CarList.csv";
        int counter = 0;
        try { //open and read the CSV file
            File file = new File(CSVfileName);
            Scanner input = new Scanner(file);
            System.out.format("%-8s%-18s%-10s%-16s%-16s%-16s\n",
                    "Car No.", "Car Name", "Seats", "Transmission", "Car Type",
                    "Rate/Day($");
            System.out.format("%-8s%-18s%-10s%-16s%-16s%-16s\n", "-------",
                    "-------", "----- ", "------------", "---------",
                    "--------");
            while (input.hasNextLine()) {
                String line = input.nextLine();
                counter++;
                String fields[] = line.split(",");
                String carNumber = fields[0];
                String carName = fields[1];
                String seats = fields[2];
                String transmission = fields[3];
                String carType = fields[4];
                String ratePerDay = fields[5];

                System.out.format("%-8s%-18s%-10s%-16s%-16s%-16s\n",
                        carNumber, carName, seats, transmission, carType,
                        ratePerDay);
            }
package carrentaltester;


public class Car {
    
    double carRate;
    String carName; 
        
    MenuDisplay carInfo = new MenuDisplay();
    
}

Answer 1

carName是Car对象的字段变量。首先必须实例化一个Car，然后访问它的carName字段。

Car car = new Car();

(...)

car.carName = fields[1];

应该实例化Car对象的位置取决于具体情况。我会把它作为一个参数传递给displayCarList。

public static void displayCarList(Car car) {
    (...)
    car.carName = fields[1];
    (...)
}

用法：

public class Car {
    double carRate;
    String carName;

    public static void main(String[] args) {
        Car car = new Car();
        MenuDisplay carInfo = new MenuDisplay(car);
    }
}

Answer 2

创建Car类的对象并设置值。然后你就可以进入。