Question

早上好！我试图理解Java中的类。我的任务是创建一个Employee类，一个Name类和一个Address类，并使用它们将信息存储到一个Array中。显然我的代码仍然是一个正在进行的工作，但我不明白如何使用Name类和Address类将值放入Array中。

特别是在我的开关（案例1）中，我想将每个属性的输入分配到数组中，但我不明白类实例是如何工作的。我曾尝试在线和在我的教科书中阅读，但没有一个解释是真的点击我。

这是我第一次接触Java类，所以任何有助于我将来应用这些概念的解释（而不仅仅是这个代码）都会非常感激。我真的想学习这一点，而不仅仅是完成一项硬件任务。提前感谢您的时间和思想！

import java.util.Scanner;

class Employee {

    String fName = " ";
    String lName = " ";
    String city = " ";
    String state = " ";

    public static void main( String [] args ) {

        int choice; //For Menu option
        Scanner input = new Scanner( System.in );
        boolean looping = true; //Loop the menu
        while(looping == true) {
            System.out.println( "1. Add New Employee" );
            System.out.println( "0. Exit" );
            System.out.print( "Choice: " );
            choice = input.nextInt();

            switch(choice) {
                case 0: {
                    System.out.println( "Goodbye." );
                    looping = false;
                    break;
                }
                case 1: {
                    Employee [] employeeInfo = new Employee[9];
                    for(int i = 0; i < employeeInfo.length ; i++) {
                        Scanner info = new Scanner( System.in );

                        System.out.print( "Enter the Employee's First Name: ");
                        employeeInfo[i].fName = info.nextLine();
                        System.out.print( "Enter the Employee's Last Name: ");
                        employeeInfo[i].lName = info.nextLine();
                        System.out.print( "Enter the Employee's City: ");
                        employeeInfo[i].city = info.nextLine();
                        System.out.print( "Enter the Employee's State: ");
                        employeeInfo[i].state = info.nextLine();
                        break;
                }
                default:
                    System.out.println( "Invalid option." );
            }
        }
    }

    class Name {

        private String fName;
        private String lName;

        //Constructors
        Name() { //no parameters

            fName = " ";
            lName = " ";
        }

        Name(String fName, String lName) { //parameters

            this.fName = fName;
            this.lName = lName;
        }

        @Override
        public String toString () {

            return "The employee's name is: " + fName + " " + lName;
        }
    }

    class Address {

        private String city;
        private String state;

        //Constructors
        Address() {

            this.city = " ";
            this.state = " ";
        }

        Address( String city, String state ) {

            this.city = city;
            this.state = state;
        }

        @Override
        public String toString (){

            return "The employee's residence is " + city + ", " + state;
        } 
    }
}

Answer 1

您的Employee[] employeeInfo = new Employee[9];创建一个可以容纳9个Employee个对象的数组，但每个元素最初都为null。您需要使用新的Employee对象填充每个对象。在for循环内，请在顶部执行此操作：

employeeInfo[i] = new Employee();

您还需要将break移出for循环，移至case的底部。否则，您的程序将只输入一个人的数据，而不是九个人的数据。

使用嵌套类和数组

1 个答案: