java从其他类访问数据

Question

我是初学者，所以请非常具体。无论如何，我这里有三个代码类，我想从c-b然后b-a访问数据，例如

class GoobyPls {
{
    private int CHealth = 20;
    private int MHealth = 20;
    private int CAgility = 10;
    private int MAgility = 10;
    private int CDefence = 5;
    private int MDefence = 5;
}   
}

class Stats {
public static void foo() {
    string Health =  CHealth + "/" + MHealth ;
    string Agility = CAgility + "/" + MAgility;
    string Defence = CDefence + "/" + MDefence;
}

}

class ViewStats {
public static void foo() {
System.out.println("Health");
                System.out.println(Health);
                System.out.println(" ");
                System.out.println("Agility");
                System.out.println(Agility);
                System.out.println(" ");
                System.out.println("Defence");
                System.out.println(Defence);
                System.out.println(" ");
  }
}

所以{}是{}，{}是{}，{}是{}

另外，我不能把它全部放在一个类中，因为最终会有一个修改器类来编辑CHealth、MHealth等等

Answer 1

首先，你不能像下面这样谈论你的私人领域

 class GoobyPls {
{
    private int CHealth = 20;  // you can't use private here
    private int MHealth = 20;   // and care on java naming conventions
    private int CAgility = 10;
    private int MAgility = 10;
    private int CDefence = 5;
    private int MDefence = 5;
}
} 

它应该是String而不是字符串

   string Health =  CHealth + "/" + MHealth ; // String not string

使用IDE进行编码，它将帮助您自己识别此类问题

Answer 2

在类中GoobyPls为每个项添加getter，如下所示：

class GoobyPls {
{
   private int CHealth = 20;

   public int getHealth(){
      return Chealth;
   }
}

然后在viewStats中执行以下操作：

GoodyPls gp = new GoobyPls();
System.out.println(gp.getHealth());

只要在需要使用私有变量时调用getter即可。或者您也可以定义公共变量，以便直接在viewStats中调用它们。但是从设计的角度来看，getter和setter更好，因为隐藏信息更好。 字段应声明为私有，除非有充分理由不这样做

Answer 3

我强烈建议您通读Java tutorial on classes and objects，这将为您的工作打下良好的基础

在类之间传递数据的最基本方法是在类中定义公共方法，其他对象可以调用这些方法来访问您的数据。例如：

public class Person {

    private String firstName; 
    private String lastName;

    public String getFirstName () {
        return firstName;
    }

    public String getLastName () {
        return lastName;
    }

}

返回值的名称为getX()的方法称为“getter”。然后，在另一个类中，您可以访问该数据，例如：

public void elsewhere () {
    Person p = new Person();
    System.out.println(p.getFirstName() + " " + p.getLastName());
}

与类通信的另一种方式是编写采用参数的方法，例如：

public void printFullName (Person p) {
    System.out.println(p.getFirstName() + " " + p.getLastName());
}

public void elsewhere () {
    Person p = new Person();
    printFullName(p);
}

您可能还希望提供方法来设置对象中的数据。这些被称为“setter”，与“getter”相对应。在Person之上构建：

public class Person {

    private String firstName; 
    private String lastName;

    public String getFirstName () {
        return firstName;
    }

    public String getLastName () {
        return lastName;
    }

    public void setFirstName (String firstName) {
        this.firstName = firstName;
    }

    public void setLastName (String lastName) {
        this.lastName = lastName;
    }

}

然后，其他对象可以修改个人的数据，例如：

public void elsewhere () {
    Person p = new Person();
    p.setFirstName("Bob");
    System.out.println(p.getFirstName()); // prints "Bob"
}

下面是一个使用上面所有内容的示例：

public void swapPersonFirstAndLastName (Person p) {
    String temporary = p.getFirstName();
    p.setFirstName(p.getLastName());
    p.setLastName(temporary);
}

public void printFullName (Person p) {
    System.out.println(p.getFirstName() + " " + p.getLastName());
}

public void example () {
    Person p = new Person();
    p.setFirstName("John");
    p.setLastName("Smith");
    swapPersonFirstAndLastName(p);
    printFullName(p); // prints Smith John
}

希望对你有帮助，祝你好运。阅读那些教程

Answer 4

在你的班上放上“能手”和“二传手”。或者将字段公开。（我不建议第二个）

class GoobyPls {

    public int getCHealth() {
        return CHealth;
    }
    public void setCHealth(int cHealth) {
        CHealth = cHealth;
    }
    public int getMHealth() {
        return MHealth;
    }
    public void setMHealth(int mHealth) {
        MHealth = mHealth;
    }
    public int getCAgility() {
        return CAgility;
    }
    public void setCAgility(int cAgility) {
        CAgility = cAgility;
    }
    public int getMAgility() {
        return MAgility;
    }
    public void setMAgility(int mAgility) {
        MAgility = mAgility;
    }
    public int getCDefence() {
        return CDefence;
    }
    public void setCDefence(int cDefence) {
        CDefence = cDefence;
    }
    public int getMDefence() {
        return MDefence;
    }
    public void setMDefence(int mDefence) {
        MDefence = mDefence;
    }
    private int CHealth = 20;
    private int MHealth = 20;
    private int CAgility = 10;
    private int MAgility = 10;
    private int CDefence = 5;
    private int MDefence = 5;
}  

然后您可以这样访问：

class Stats {
public static void foo() {
GoobyPls gbp=new GoobyPls();
    string Health =  gbp.getCHealth + "/" + MHealth ;
    string Agility = gbp.getCAgility + "/" + MAgility;
    string Defence = gbp.getCDefence + "/" + MDefence;
}

Answer 5

如果要访问类外部的私有变量，必须使用下面的getter方法

class GoobyPls {
private int CHealth = 20;
private int MHealth = 20;
private int CAgility = 10;
private int MAgility = 10;
private int CDefence = 5;
private int MDefence = 5;
public int getCHealth() {
    return CHealth;
}
public int getMHealth() {
    return MHealth;
}
public int getCAgility() {
    return CAgility;
}
public int getMAgility() {
    return MAgility;
}
public int getCDefence() {
    return CDefence;
}
public int getMDefence() {
    return MDefence;
}
}  

下面是你的国家班

class Stats {
public static void foo() {
GoobyPls g=new GoobyPls();
int Health =  g.getCHealth() / g.getMHealth() ;
int Agility = g.getCAgility() / g.getMAgility();
int Defence = g.getCDefence() / g.getMDefence();
}

在viewstat类的foo()方法中，您可以通过State.Health、State.Agility和State.Defence访问about值