Java 处理对象';s范围
我试图用Java编写一个游戏,其中包含一个Java 处理对象';s范围,java,oop,Java,Oop,我试图用Java编写一个游戏,其中包含一个Player类,该类有两个子类:HumanPlayer和ComputerPlayer。我想让用户选择与哪个玩家比赛,一旦选择,就创建相关的对象并进行比赛 因为对象是在if语句中创建的,所以编译器不允许我在if范围之外执行任何操作。在其他情况下,我会在类的范围内创建对象,但在这种情况下,我无法提前知道要创建哪个对象(人/计算机) 以下是一些用于说明的代码: public class Player { private String name;
Player
类,该类有两个子类:HumanPlayer
和ComputerPlayer
。我想让用户选择与哪个玩家比赛,一旦选择,就创建相关的对象并进行比赛
因为对象是在if语句中创建的,所以编译器不允许我在if范围之外执行任何操作。在其他情况下,我会在类的范围内创建对象,但在这种情况下,我无法提前知道要创建哪个对象(人/计算机)
以下是一些用于说明的代码:
public class Player {
private String name;
public String getName(){
return name;
}
}
public class HumanPlayer extends Player {
public void play(){
System.out.println("Human playing");
}
}
public class ComputerPlayer extends Player {
public void play(){
System.out.println("Computer playing");
}
}
import java.util.Scanner;
public class PlayerDriver {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.println("Please type 1 for human, 2 for computer");
int selection = in.nextInt();
if (selection==1){
HumanPlayer player = new HumanPlayer();
} else if (selection==2){
ComputerPlayer player = new ComputerPlayer();
} else {
throw new IllegalArgumentException("invalid answer");
}
Player.play(); //can't do that
}
}
利用
假设
Player
类有一个play()
方法。我看不是。将您的类Player
更改为具有可覆盖的play()
方法,您可以在子类型中覆盖该方法。完美!谢谢你的快速回复
Player player = null; // player should never be null as you would have thrown an exception, but for the sake of completeness
if (selection == 1){
player = new HumanPlayer();
} else if (selection == 2){
player = new ComputerPlayer();
} else {
throw new IllegalArgumentException("invalid answer");
}
player.play();