在main中声明的数组不能在后续方法中访问- Java

Question

我在main方法中声明并初始化了一个数组。我无法在同一程序中的任何后续方法中访问该数组。这正常吗？

有没有办法让我在后续的方法中只需调用数组就能访问该数组？或者，我是否必须为每个新方法重新声明和初始化数组？

谢谢!

这就是我的程序现在的样子，在main方法内部和外部都有数组声明。

 import java.io.*; 
 import java.util.*; 

public class useHamayelSajaEmployee 
{
    final int MAX_EMPLOYEES = 1000;
    HamayelSajaEmployee []emps = new HamayelSajaEmployee[MAX_EMPLOYEES]; 

    public static void main(String[]args) throws IOException 
    {
        Scanner scan = new Scanner(System.in); //scanner for reading from keyboard

        final int MAX_EMPLOYEES = 1000;
        HamayelSajaEmployee []emps = new HamayelSajaEmployee[MAX_EMPLOYEES]; 

        File file = new File("empList.txt");
        Scanner scan2 = new Scanner(file); //scanner for reading from file

        String divisionTitle = scan2.nextLine(); 
        int numOfEmps;

        for (int k = 0; k < 1000; k++) //for loop to set all the objects in array to constructor values
                    {
                        emps [k] = new HamayelSajaEmployee();
                    }

        int lastCount = 0; 

            while(!divisionTitle.equals("END_OF_FILE"))
        {
            System.out.println(divisionTitle + '\n');
            numOfEmps = scan2.nextInt();

            for (int i = lastCount; i < numOfEmps + lastCount; i++) //instead of starting from the 0 point and writing over the objects in array, starting from point we stopped with lastCount
            {
                HamayelSajaEmployee emp1 = new HamayelSajaEmployee();

                emp1.SetDivisionTitle(divisionTitle);

                String lastName = scan2.next();
                System.out.print(lastName + "\t" ); 
                emp1.SetLastName(lastName);

                String firstName = scan2.next();
                System.out.print(firstName + "\t");
                emp1.SetFirstName(firstName);

                int yearsInCompany = scan2.nextInt();
                System.out.print(yearsInCompany + "\t" );
                emp1.SetYearsInCompany(yearsInCompany);

                double salary = scan2.nextDouble();
                System.out.print(salary + "\t"  + "\t" );
                emp1.SetSalary(salary);

                String status = scan2.next();
                char status1 = status.charAt(0);
                System.out.print(status1 + "\t" );
                emp1.SetStatus(status1);

                String section = scan2.nextLine();
                System.out.println(section);
                emp1.SetSection(section);


                emps [i]= emp1;

            }
            System.out.println('\n'); //prints extra line between divisions for clarity
            divisionTitle = scan2.next();
            lastCount = numOfEmps + lastCount;
        }

        for (int i = 0; i < 1000; i++)
        { 
            if(!emps[i].GetDivisionTitle().equals("noDivsionTitle"))//so that no empty slots in array print
            {System.out.println(emps[i]);}
        }


        System.out.print("Enter 'M' to go to the Menu or 'Q' to Quit");
        String newPlace = scan.next();
        char newPlace1 = newPlace.charAt(0);


        if(newPlace1 == 'M' || newPlace1 == 'm')
        {menu();}

        if (newPlace1 == 'Q' || newPlace1 == 'q')
        {finalStats();}

        else
            {
            while (!(newPlace1 == 'M' || newPlace1 == 'm' || newPlace1 == 'Q' || newPlace1 == 'q'))
                {
            System.out.println("ERROR");
            System.out.println("Please try again.");

            System.out.print("Enter 'M' to go to the Menu or 'Q' to Quit");
            newPlace = scan.next();
            newPlace1 = newPlace.charAt(0);
            if(newPlace1 == 'M' || newPlace1 == 'm')
            {menu();}

            if (newPlace1 == 'Q' || newPlace1 == 'q')
            {finalStats();}
                }
            }

    }

这是另一个方法的样子(我直接将初始化和数组声明从main复制/粘贴到这个方法中。

public static boolean listAll()
    {
        /* method meant to list all the employees names, years in company, salaries, statuses, and sections as read in from file*/
        File file = new File("empList.txt");
        Scanner scann = new Scanner(file);

        String divisionTitle = scann.nextLine(); 
        int numOfEmps;

        final int MAX_EMPLOYEES = 1000;
        HamayelSajaEmployee []emps = new HamayelSajaEmployee[MAX_EMPLOYEES]; 

        for (int k = 0; k < 1000; k++) //for loop to set all the objects in array to constructor values
                    {
                        emps [k] = new HamayelSajaEmployee();
                    }

        int lastCount = 0; 

            while(!divisionTitle.equals("END_OF_FILE"))
        {
            System.out.println(divisionTitle + '\n');
            numOfEmps = scann.nextInt();

            for (int i = lastCount; i < numOfEmps + lastCount; i++) //instead of starting from the 0 point and writing over the objects in array, starting from point we stopped with lastCount
            {
                HamayelSajaEmployee emp1 = new HamayelSajaEmployee();

                emp1.SetDivisionTitle(divisionTitle);

                String lastName = scann.next();
                System.out.print(lastName + "\t" ); 
                emp1.SetLastName(lastName);

                String firstName = scann.next();
                System.out.print(firstName + "\t");
                emp1.SetFirstName(firstName);

                int yearsInCompany = scann.nextInt();
                System.out.print(yearsInCompany + "\t" );
                emp1.SetYearsInCompany(yearsInCompany);

                double salary = scann.nextDouble();
                System.out.print(salary + "\t"  + "\t" );
                emp1.SetSalary(salary);

                String status = scann.next();
                char status1 = status.charAt(0);
                System.out.print(status1 + "\t" );
                emp1.SetStatus(status1);

                String section = scann.nextLine();
                System.out.println(section);
                emp1.SetSection(section);

                emps [i]= emp1;

            }
            System.out.println('\n'); //prints extra line between divisions for clarity
            divisionTitle = scann.next();
            lastCount = numOfEmps + lastCount;
        }

        for (int i = 0; i < 1000; i++)
        { 
            if(!emps[i].GetDivisionTitle().equals("noDivsionTitle"))//so that no empty slots in array print
            {System.out.println(emps[i]);}
        }

        return true;
    }

Answer 1

在方法(如main方法)中本地声明的数组只能在该方法中访问。

您可以执行以下任一操作：

1. 使数组成为您的类的实例或类成员，这将允许您的类的其他方法访问它。

或

1. 将其作为参数传递给任何需要它的方法。

要将数组作为参数传递，请执行以下操作：

public static void main(String[]args) throws IOException 
{
    ...
    HamayelSajaEmployee[] emps = ...
    ...
    listAll (emps);
}

Ans someMethod将如下所示：

public static boolean listAll (HamayelSajaEmployee[] emps)
{
    for (int i = 0; i < emps.length; i++) { 
        if(!emps[i].GetDivisionTitle().equals("noDivsionTitle")) {
            System.out.println(emps[i]);
        }
    }

    return true;
}

Answer 2

这与“作用域”的概念有关。以以下类为例：

public class SomeClass {
    int x = 3;
    public void SomeMethod() {
        int y = 5;
        if(x != y) {
            int z = x + y;
        }
    }
}

"x“可以在SomeClass中的任何地方访问，y只能在SomeMethod中访问，z只能在if语句中访问。这样想:当你声明一个变量时，它只能在它周围最紧凑的两个{}中访问。这是作用域概念的基础。现在，一旦你开始使用不同的变量修饰符(比如"public")，你就可以开始改变给定变量/方法的作用域。

为了解决不能在另一个方法中访问在一个方法中创建的数组的问题，我建议类似于"x“在我的示例类中的位置来声明该数组。然后在整个类中都可以访问它。

如果您感兴趣，在Oracle的网站上有一篇关于访问控制和修饰符的文章，但对于这个特定的问题，这篇文章并不是必需的：https://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html

编辑:删除了SomeMethod的" static“修饰符，这样我们就不会对非静态变量进行静态引用。