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java - 使用静态变量查找数组中的元素数

问题描述

我正在开发一个车辆信息系统的项目。我已将所有实例存储在一个数组中，并且必须使用静态变量打印出其中的元素/实例的数量。我尝试了下面的代码，但我猜我一直得到 0，因为它引用了类中定义的计数（初始化为 0），而不是构造函数中具有实例总数的计数。我怎样才能解决这个问题？

package edu.uga.cs1302.vehicles;

import java.util.Scanner;

public class vehicleInstancesAndMenu {
static int count;
    
public vehicleInstancesAndMenu() {
    menu();
}//constructor

public void vehicles() {
    Vehicle[] vehicles = new Vehicle[15];
    vehicles[0] = new Airplane("Airbus A220-100", "Delta Airlines", "2019", 2, 120, 300, 221, 250);
    vehicles[1] = new Airplane("Airbus A319-100", "Delta Airlines", "2018", 2, 200, 450, 319, 300);
    vehicles[2] = new Airplane("Airbus A320-200", "Delta Airlines", "2018", 2, 220, 500, 320, 320);
    
    vehicles[3] = new Automobile("Corolla LE", "Toyota", "2020", 300, 6, 150);
    vehicles[4] = new Automobile("Civic SE", "Honda", "2018", 310, 6, 160);
    vehicles[5] = new Automobile("Sentra", "Nissan", "2019", 360, 6, 200);
    
    vehicles[6] = new Ship("APM - Maersk", "Maersk", "1904", 400000, "Carnival",2695, 35);
    vehicles[7] = new Ship("MSC", "Mediterranean Shipping Company", "1970", 30000 ,"Mediterranean Shipping Company",2565, 32);
    vehicles[8] = new Ship("COSCO", "China Ocean Shipping Company", "1990", 650000, "China Ocean Shipping Company",36201, 40);
    
    vehicles[9] =  new Tesla("Tesla Model 3", "Tesla", "2020", 1, 250, 200, 6, 300);
    vehicles[10] = new Tesla("Tesla Model S", "Tesla", "2020", 1, 300, 220, 6, 390);
    vehicles[11] = new Tesla("Tesla Model Y", "Tesla", "2020", 1, 400, 360, 6, 420);
    
    vehicles[12] = new BatMobile("Model A","Wayne Industries", "2020", 4 , 300, 600 , 40000, "Wayne Industries", 500, 320);
    vehicles[13] = new BatMobile("Model C", "Wayne Industries", "2019", 3 , 290, 400, 32000, "Wayne Industries", 450, 310);
    vehicles[14] = new BatMobile("Model T", "Wayne Industries", "2018",3 , 250, 360, 280000, "Wayne Industries", 370, 310);

for(int i = 0; i < vehicles.length; i++) {
        count = vehicles.length;
    //System.out.println(vehicles[i] ); 
}//for
    System.out.println(count);
    }//vehicles

public void menu() {
    Scanner scan = new Scanner(System.in);
    String response;
    
    System.out.println("Welcome! \n1 - To see how many vehicles are in the system\n2 - To see the name and the class of each vehicle\n3 - To see which vehicles can fly.\n4 - To see which vehicles can float.\n5 - To see which vehicles can fly and float.\n6 - To see a description of each vehicle.\nh - to see brief help information for your system.\nq - To terminate the program.");
        response = scan.nextLine();
    
    switch(response) {
        case "1":
            if(response.equals("1")) {
                System.out.println(vehicleInstancesAndMenu.count);
            }
    }
}






}//vehicleInstancesAndMenu

标签： javaarraysscopestaticglobal-variables

解决方案

您应该能够通过在函数中包含vehicle(); 在您的行menu()之前的某个位置来解决此问题。System.out.println('..');目前该函数从未被调用，因此它没有计算任何东西。而不是在函数中使用循环vehicle()，只需count = vehicles.length;按照注释中的说明进行设置。

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