java如何从另一个类访问变量getter和setter

Question

我有三节课

public class GameInfo 
{
  private  int num;
  public void setNum(int num){
         this.num=num;
    }
  public int getNum(){
         return num; 
   }
}

public class NewGame
{ 
  public void foo(){
    GameInfo g = new GameInfo();
    g.setNum(10);
}
}

public class StartGame()
{
   //i want to access the num in GameInfo being set by NewGame class. How to do that? 

}

如果我在StartName类中创建GameInfo类的新对象，如

GameInfo g = new GameInfo();
int number = g.getnum(); //it returns 0

我想在数字变量中得到10

Answer 1

GameInfo的私有成员num按默认值初始化为0。如果要返回其他内容，必须在g.getNum()之前调用g.setNum(10)

Answer 2

Sinenum变量是GameInfo类的实例成员，因此每次创建GameInfo的新对象时，num的值都将设置为默认值，即0

因此，为了获得10作为getnum（）方法的返回，首先需要在同一对象引用上调用setter方法作为setnum（10）

public class StartGame() {
    NewGame newGame = new NewGame();
    newGame.foo();  // It sets 10, but this value will only be accessible from your NewGame's instance.
    GameInfo info = new GameInfo();
    info.setnum(10);  // It sets num to 10
    int number = info.getnum(); //it returns 10
}