如何在主类内的方法中调用对象数组？

Question

我正在尝试在 searchByCompany() 方法中使用 IcecreamArray[] 来按公司名称打印冰淇淋信息，但它给了我一个错误数组不存在。

错误： 创建局部变量 IcecreamArray。另外，我怎样才能让我的代码更有效率？

public class MainIcecream {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Icecream[] IcecreamArray = new Icecream[5];
        for (int i = 0; i < 5; i++) {
            IcecreamArray[i] = new Icecream();
            System.out.println("Enter Icecream type " + i + " : ");
            IcecreamArray[i].setIcecreamType(sc.next());
            System.out.println("Enter Icecream Company " + i + " : ");
            IcecreamArray[i].setIcecreamCompany(sc.next());
            System.out.println("Enter Icecream Price " + i + " : ");
            IcecreamArray[i].setIcecreamPrice(sc.nextDouble());
        }

    public static void searchByCompany(String s){
        for (int i = 0; i < 5; i++) {
            if(s.equals(IcecreamArray[i].getIcecreamCompany())){
                System.out.println(IcecreamArray[i].getIcecreamType());
                System.out.println(IcecreamArray[i].getIcecreamCompany());
                System.out.println(IcecreamArray[i].getIcecreamPrice());
            } 
        }
    }

    public static class Icecream {

        private String icecreamType;
        private String icecreamCompany;
        private double icecreamPrice;

        public String toString(){
            String str , t , c;
            double p;
            t = icecreamType;
            c = icecreamCompany;
            p = icecreamPrice;
            str = "Icecream type: " + t + "\nManufacturer: " + c + "\nPrice: " + p;
            return str;
        }
        public void setIcecreamType(String t) {
            icecreamType = t;   
        }
        public void setIcecreamCompany(String c){
            icecreamCompany = c;
        }
        public void setIcecreamPrice(double p){
            icecreamPrice = p;
        }
        String getIcecreamType(){
            return icecreamType;
        }
        String getIcecreamCompany(){
            return icecreamCompany;
        }
        double getIcecreamPrice(){
            return icecreamPrice;
        }
    }
}

Answer 1

试试这样的。希望它能解决您的问题：----

import java.util.Scanner;

public class MainIcecream {

    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Icecream[] IcecreamArray = new Icecream[5];
        for (int i = 0; i < IcecreamArray.length; i++) {
            System.out.println("Enter Iceiceicecream Price " + i + " : ");
            double icecream_price = sc.nextDouble();
            System.out.println("Enter Icecream type " + i + " : ");
            String icecream_type = sc.next();

            System.out.println("Enter Icecream Company " + i + " : ");
            String icecream_company = sc.next();
            IcecreamArray[i] = new Icecream(icecream_type, icecream_company, icecream_price);
            
        }
        sc.nextLine();
        System.out.println("Enter Icecream Company  to retrieve all ");
        String icecreamCompany = sc.nextLine();
        searchByCompany(icecreamCompany, IcecreamArray);
        sc.close();
    }

    public static void searchByCompany(String s, Icecream[] icecreamArray) {
        boolean flag = false;
        for (int i = 0; i < icecreamArray.length; i++) {

            if (s.equals(icecreamArray[i].getIcecreamCompany())) {
                flag = true;
                System.out.println(icecreamArray[i].getIcecreamType());
                System.out.println(icecreamArray[i].getIcecreamCompany());
                System.out.println(icecreamArray[i].getIcecreamPrice());
            }
        }
        if (!flag) {
            System.out.println("record not found");
        }

    }

    public static class Icecream {

        private String icecreamType;
        private String icecreamCompany;
        private double icecreamPrice;

        public Icecream(String icecream_type, String icecream_company, double icecream_price) {
            this.icecreamType = icecream_type;
            this.icecreamCompany = icecream_company;
            this.icecreamPrice = icecream_price;
        }

        public String toString() {
            String str, t, c;
            double p;
            t = icecreamType;
            c = icecreamCompany;
            p = icecreamPrice;
            str = "Icecream type: " + t + "\nManufacturer: " + c + "\nPrice: " + p;
            return str;
        }

        public void setIcecreamType(String t) {
            icecreamType = t;
        }

        public void setIcecreamCompany(String c) {
            icecreamCompany = c;
        }

        public void setIcecreamPrice(double p) {
            icecreamPrice = p;
        }

        String getIcecreamType() {
            return icecreamType;
        }

        String getIcecreamCompany() {
            return icecreamCompany;
        }

        double getIcecreamPrice() {
            return icecreamPrice;
        }
    }
}

Answer 2

我通过将 IcecreamArray 作为参数传递给 searchByCompany 来修复代码。

这是最终代码：

public class MainIcecream {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Icecream[] IcecreamArray = new Icecream[5];
        for (int i = 0; i < 5; i++) {
            IcecreamArray[i] = new Icecream();
            System.out.println("Enter Icecream type " + i + " : ");
            IcecreamArray[i].setIcecreamType(sc.next());
            System.out.println("Enter Icecream Company " + i + " : ");
            IcecreamArray[i].setIcecreamCompany(sc.next());
            System.out.println("Enter Icecream Price " + i + " : ");
            IcecreamArray[i].setIcecreamPrice(sc.nextDouble());
        }
}
    public static void searchByCompany(Icecream IcecreamArray[]) {
        System.out.println("Enter manufacturer to search for icecream information: ");
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        for (int i = 0; i < 5; i++) {
            if (s.equals(IcecreamArray[i].getIcecreamCompany())) {
                System.out.println("Icecream Type: " + IcecreamArray[i].getIcecreamType());
                System.out.println("Icecream Company: " + IcecreamArray[i].getIcecreamCompany());
                System.out.println("Icecream Price: $" + IcecreamArray[i].getIcecreamPrice());
            }
        }
    }
    public static class Icecream {

        private String icecreamType;
        private String icecreamCompany;
        private double icecreamPrice;

        public String toString(){
            String str , t , c;
            double p;
            t = icecreamType;
            c = icecreamCompany;
            p = icecreamPrice;
            str = "Icecream type: " + t + "\nManufacturer: " + c + "\nPrice: " + p;
            return str;
        }
        public void setIcecreamType(String t) {
            icecreamType = t;   
        }
        public void setIcecreamCompany(String c){
            icecreamCompany = c;
        }
        public void setIcecreamPrice(double p){
            icecreamPrice = p;
        }
        String getIcecreamType(){
            return icecreamType;
        }
        String getIcecreamCompany(){
            return icecreamCompany;
        }
        double getIcecreamPrice(){
            return icecreamPrice;
        }
    }
}

Answer 3

您已在 main 方法内声明并初始化 IcecreamArray，因此 main IcecreamArray 外部不存在。

您可以将 IcecreamArray 作为参数传递给 searchByCompany，或者在 main 之外将其声明为静态变量

我仔细查看了您的代码，您尝试在 main 中声明 searchByCompany 无效。您不能在另一个方法中声明一个方法。下面我提供了一个你可以做什么的例子

public class MainIcecream {

    private static Icecream[] IcecreamArray = new Icecream[5];

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        for (int i = 0; i < 5; i++) {
            IcecreamArray[i] = new Icecream();
            System.out.println("Enter Icecream type " + i + " : ");
            IcecreamArray[i].setIcecreamType(sc.next());
            System.out.println("Enter Icecream Company " + i + " : ");
            IcecreamArray[i].setIcecreamCompany(sc.next());
            System.out.println("Enter Icecream Price " + i + " : ");
            IcecreamArray[i].setIcecreamPrice(sc.nextDouble());
        }

        System.out.println("Enter company name to search");
        searchByCompany(sc.next());
    }

    private static void searchByCompany(String s) {
        for (int i = 0; i < 5; i++) {
            if (s.equals(IcecreamArray[i].getIcecreamCompany())) {
                System.out.println(IcecreamArray[i].getIcecreamType());
                System.out.println(IcecreamArray[i].getIcecreamCompany());
                System.out.println(IcecreamArray[i].getIcecreamPrice());
            }
        }
    }
}

Answer 4

您的程序有一些编译器错误。除此之外，IcecreamArray 在main 方法内初始化，它的作用域在该方法内。它对其他方法不可见，因为它不存在于它们的上下文中。

这是您的选择，

1. 将数组作为参数传递给searchByCompany 方法，所以 searchByCompany(String s, Icecream[] array)

2. 使数组成为类的字段，以便其他人可以访问它 方法（在这种情况下使其成为静态字段），所以public static Icecream[] IcecreamArray = new Icecream[5];