java从另一个类访问变量

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我在从另一个类访问字符串时遇到问题，我不知道我可以让它变得更加简单。例如，我有一个名为“Person”的类，并且有一个字符串名称。我通过构造函数以及直接设置名称的“名称”。我还有另一个名为 Loan 的类，我还没有尝试访问任何内容。我的最后一个类叫做“App”，一切都在那里完成。

顺便说一句 - Person 是我的父类(super class)，Loan 扩展了 Person，App 扩展了 Loan，它们都在同一个包中。

现在，在我的应用程序类中，我尝试访问我创建的唯一人员对象的字符串“名称”。我再次通过构造函数直接分配了名称，但不知何故这不起作用。最初我的名字集是 protected ，因为我是这样理解的:protected = 访问同一类、同一包或子类中的方法/变量即使在我公开我的字符串之后，它仍然无法工作。我完全迷失了......

当我输入时

  System.out.println(omid.name);

它说它无法解析为变量，我需要创建一个本地变量。

谢谢!

这是我的 Person 代码:

package Programs;

public class Person {
    public String name;
    protected int age;
    protected int id;
    protected String status;
    protected int alienNumber;
    protected int socialSecurityNumber;

    Person()
    {

    }

    Person(String name, int age, int id)
    {
        this.name = name;
        this.age = age;
        this.id = id;
    }



    public void setid(int id)
    {
        if(id >= 100000)
        {
            this.socialSecurityNumber = id;
            System.out.println("You are now a citizen " + name);
            System.out.println("Social Security Number: " + socialSecurityNumber);
        }
        else
        {
            System.out.println("Sorry " + name + " you do not meet the qualitifactions for citizenship");
            alienNumber = id;
            System.out.println("You alien number is: " + alienNumber);

        }
    }



    public String toString()
    {
        if(id >=99000 )
        {
            status = "citizen";
        }
        else
        {
            status = "immigrant";
        }

        return "Name: " + name + 
                "Age: " + age + 
                "Id: " + id +
                "Status " + status;
        }
public static void main(String[] args)
{
    Person omid = new Person("omid nassir", 28, 120000);
    omid.name = "omid";
}




}

贷款代码

package Programs;

import Programs.Person;


public class Loan extends Person{


    public static final int LOANAMOUNT1 = 250000;
    public static final int LOANAMOUNT2 = 500000;
    public static final int LOANAMOUNT3 = 750000;
    public static final int LOANAMOUNT4 = 1000000;
    public int income;
    public int loanRequested;


    Loan(int income, int socialSecurityNumber, int loanRequested)
    {
        this.income = income;
        this.socialSecurityNumber = socialSecurityNumber;
        this.loanRequested = loanRequested;
    }


    public void applyForLoan(String name, int socialSecurityNumber, int income, int loanAmount)
    {
     int obtainable = LOANAMOUNT1 / 4;
        if(socialSecurityNumber >= 99999)
        {
            if(income > obtainable)
            {
                obtainable = loanAmount;
                System.out.println("Congradulations " + name + " you are eligible for loan amount of " + loanAmount);
            }
        }
        else if(socialSecurityNumber <=99999)
        {
            obtainable = LOANAMOUNT1;
            System.out.println("Sorry " + name + " in order to qualify for " + loanAmount + " you need to be"
                    + " a citizen and have a minimum income of " + obtainable);
            System.out.println("Loan amount granted: " + LOANAMOUNT1);
        }
    }


}

应用程序代码

package Programs;

public class App extends Person {

        public static void main(String[] args)
    {
        System.out.println(omid.name);
    }


}

Answer 1

您需要在App的main方法中定义omid。您在 Person 的 main 中定义了 omid，但无法访问此变量，因为这是一个完全不同的作用域。您可能想阅读static及其语义。