访问其他类的数据

Question

我是初学者，所以请非常具体。无论如何，我在这里有三个代码类，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GoobyPls 是a，Stats 是b 和ViewStats 是c

我也不能把它全部放在一个类中，因为最终会有一个修饰类来编辑CHealth、MHealth 等

Answer 1

在您的班级GoobyPls 中为每个项目添加 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());

当您想使用私有变量时，只需调用 getter。或者也可以定义变量public，这样就可以直接在viewStats中调用。但是从设计的角度来看，getter 和 setter 更好，因为隐藏信息更好。 除非有充分的理由不这样做，否则应将字段声明为私有。

Answer 2

如果要在类外访问私有变量，必须使用如下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 State 类

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

Answer 3

我强烈建议您通读Java tutorial on classes and objects，这将为您提供良好的工作基础。

在类之间传递数据的最基本方法是在您的类中定义公共方法，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;
    }

}

名称如getX() 并返回值的方法称为“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法是编写带参数的方法，例如：

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

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

您可能还想提供方法来设置对象中的数据。这些被称为“setter”，是“getter”的对应物。以Person 为基础：

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，其他对象可以修改一个人的数据，例如：

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

这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
}

希望对您有所帮助，祝您好运。阅读那些教程！

Answer 4

首先你不能像下面这样私有字段

 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 进行编码将帮助您自行识别此类问题。

Answer 5

将 getter 和 setter 放到你的类中。或者公开字段。（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;
}  

然后你可以这样访问：

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;
}